Estimation of self-funded human papillomavirus vaccine recipients from Japan's previously assumed "unvaccinated generation".

Precise vaccination data is essential to accurately estimate the effectiveness of the human papillomavirus (HPV) vaccine against HPV-related cancers. In Japan, the number of subsidized HPV vaccinations can be tracked through registries, but the number of self-funded vaccinations has not been tracked. The number of individuals who chose to receive the vaccine at their own expense, despite being ineligible for public subsidies due to their age, is unknown and has been nominally considered to be zero. Our aim is to produce a more accurate estimate of this number using recently released proprietary data. First, we estimated the total number of self-funded HPV vaccinations occurring from 2010 to 2012 using public data from the Ministry of Health, Labour and Welfare and our previously reported data on the number of HPV vaccinations eligible for public subsidy. Second, using proprietary data from the vaccine manufacturer, we calculated the distribution of self-funded vaccination shots by age. Finally, we combined these data to estimate the number of self-funded HPV vaccinations by birth fiscal year (FY) relative to a yearly reference population. We found that 78,264 individuals born in FY1993 and 58,190 born in FY1992 self-funded their vaccinations, representing 13.6% and 10.0% of the reference population, respectively. Additionally, we found that 5%-10% of individuals born from FY1986 to FY1991 self-funded their vaccinations. Our study revealed for the first time that a certain number of individuals from the "HPV unvaccinated generation," ineligible for subsidies due to age restrictions, chose to self-fund their vaccinations.

Prediction of deciduous teeth eruption in Brazilian children: A cross-sectional study nested in a prospective birth cohort (BRISA).

BACKGROUND: Dental eruption is part of a set of children´s somatic growth phenomena. The worldwide accepted human dental eruption chronology is still based on a small sample of European children. However, evidence points to some population variations with the eruption at least two months later in low-income countries, and local standards may be useful. So, this study aimed to predict deciduous teeth eruption from 12 months of age in a Brazilian infant population. METHODS: We developed a cross-sectional study nested in four prospective cohorts - the Brazilian Ribeirão Preto and São Luís Cohort Study (BRISA) - in a sample of 3,733 children aged 12 to 36 months old, corrected by gestational age. We made a reference curve with the number of teeth erupted by age using the Generalized Additive Models for location, scale, and shape (GAMLSS) technique. The explanatory variable was the corrected children´s age. The dependent variable was the number of erupted teeth, by gender, evaluated according to some different outcome distributional forms. The generalized Akaike information criterion (GAIC) and the model residuals were used as the model selection criterion. RESULTS: The Box-Cox Power Exponential method was the GAMLSS model with better-fit indexes. Our estimation curve was able to predict the number of erupted deciduous teeth by age, similar to the real values, in addition to describing the evolution of children's development, with comparative patterns. There was no difference in the mean number of erupted teeth between the sexes. According to the reference curve, at 12 months old, 25% of children had four erupted teeth or less, while 75% had seven or fewer and 95% had 11 or fewer. At 24 months old, 5% had less than 12, and 75% had 18 or more. At 36 months old, around 50% of the population had deciduous dentition completed (20 teeth). CONCLUSION: The adjusted age was an important predictor of the number of erupted deciduous teeth. This outcome can be a variable incorporated into children's growth and development curves, such as weight and height curves for age to help dentists and physicians in the monitoring the children's health.

A multivariate method for estimating mortality rates among children under 5 years from health and social indicators in Iraq.

BACKGROUND: Many reports on Iraq suggest that a rise in rates of death and disease have occurred since the Gulf War of January/February 1991 and the economic sanctions that followed it. METHODS: Four preliminary models, based on unadjusted projections, were developed. A logistic regression model was then developed on the basis of six social variables in Iraq and comparable information from countries in the State of the World's Children report. Missing data were estimated for this model by a multiple imputation procedure. The final model depends on three socio-medical indicators: adult literacy, nutritional stunting of children under 5 years, and access to piped water. RESULTS: The model successfully predicted both the mortality rate in 1990, under stable conditions, and in 1991, following the Gulf War. For 1996, after 5 years of sanctions and prior to receipt of humanitarian food via the oil for food programme, this model shows mortality among children under 5 to have reached an estimated 87 per 1000, a rate last experienced more than 30 years ago. CONCLUSIONS: Accurate and timely estimates of mortality levels in developing countries are costly and require considerable methodological expertise. A rapid estimation technique like the one developed here may be a useful tool for quick and efficient estimation of mortality rates among under 5 year olds in countries where good mortality data are not routinely available. This is especially true for countries with complex humanitarian emergencies where information on mortality changes can guide interventions and the social stability to use standard demographic methods does not exist.

Zero growth: long-term effect of China's family planning program.

PIP: Using data gathered from a 1995 1% sampling survey conducted by the State Statistical Bureau, a simulation study, spanning from 1995 to 2100, was conducted to estimate population trends in China. Fertility rates are projected along a low-, medium-, and high-variant line. The low-variant projection shows that China's population will peak at 1.402 billion in 2026 and then decline to about 0.8 billion at the end of the 2100s. The medium-variant projection shows that the total population will peak at 1.442 billion in 2030 and decline to 1.033 billion at the end of the century. The high-variant projection, on the other hand, indicates that China's population will top at 1.550 billion in 2045. At the end of the century, the medium age will reach 48.24, 44.81, and 39.76, respectively, for the low-, medium-, and high-variant projections. Moreover, the working-age population (males aged 16-59 years and females aged 16-54 years) will peak at 0.870 billion in 2016 and then begin to decline slowly. Total population, age structure, and labor resources will have different impacts on China's population development in the 21st century. Thus, policy-makers should consider the following four issues when making decisions: 1) pressure of population growth on resources and environment; 2) employment of the working-age population; 3) the preparedness for an aging population; and 4) the fertility desires of the public.^ieng

How many, how old, how soon?

PIP: This article highlights the population projections for the UK to 2066 and their health implications. The changes in the demographic age structure of human populations have dual implications. Although they represent accomplishments in social and health development considering the fact that more individuals are able to live until old age, these changes also bring new demands that affect all aspects of society, including employment, taxation, pension, education, and health. Age specific population projections presented were obtained from the Office for National Statistics. It is projected that the total number of people aged 60 years and older will rise from 12 million in 2001 to 18.6 million in 2031 and the number of individuals suffering with chronic diseases and disabilities will see a three-fold increase. Although these projections rely on assumptions and are subject to some changes, it is made clear that the proportion of the population aged 65 and above will continue to increase substantially over the next decades. These population trends will have a large impact on the health and health care needs of the population. Thus, there is a need to develop and plan institutions and policies that address the demands of the aging population. Understanding and identification of the causes and prevention of conditions that could result to serious disabilities must be a high priority.^ieng

The comparison of mixed distribution analysis with a three-criteria model as a method for estimating the prevalence of iron deficiency anaemia in Costa Rican children aged 12-23 months.

BACKGROUND: A maximum likelihood method of mixed distribution analysis (MDA) is presented as a method to estimate the prevalence of iron deficiency anaemia (IDA) in Costa Rican infants 12-23 months old. MDA characterizes the parameters of the admixed distributions of iron deficient anaemics and non-iron-deficient-anaemics (NA) from the frequency distribution of haemoglobin concentration of the total sample population. METHODS: Data collected by Lozoff et al. (1986) from 345 Costa Rican infants 12-23 months old were used to estimate the parameters of the IDA and NA haemoglobin distributions determined by MDA and the widely used three-criteria model of iron deficiency. The estimates of the prevalence of IDA by each of the methods were compared. The sensitivity and specificity of MDA compared to diagnosis by the three-criteria method were assessed. Simulations were carried out to assess the comparability of MDA and the three-criteria method in low and high prevalence scenarios. RESULTS: The mean and standard deviation (SD) of the NA haemoglobin distribution determined by both methods was 12.1 +/- 1.0 g/dL. The IDA haemoglobin distribution determined by MDA had a mean and SD of 10.2 +/- 1.3 g/dL while the IDA distribution by the three-criteria method had a mean and SD of 10.4 +/- 1.3 g/dL. The prevalences of IDA as estimated by MDA and the three-criteria method were 24% and 29%, respectively. The sensitivity and specificity of MDA were 95% and 97%, respectively. The performance of MDA was similar to the three-criteria method at a simulated high prevalence of IDA and less similar at a low prevalence of IDA. CONCLUSIONS: Compared to the reference three-criteria method MDA provides a more accurate estimate of the true prevalence of IDA than the haemoglobin cutoff method in a population of children aged 12-23 months with a moderate to high prevalence of IDA. MDA is a less costly method for estimating the severity of IDA in populations with moderate to high prevalences of IDA, and for assisting in the design, monitoring and evaluation of iron intervention programmes.

PIP: A maximum likelihood method of mixed distribution analysis (MDA) is presented as a method to estimate the prevalence of iron deficiency anemia (IDA) in Costa Rican infants aged 12-23 months old. MDA characterizes the parameters of the ad-mixed distributions of iron deficient anemics and non-iron-deficient anemics (NA) from the frequency distribution of hemoglobin concentration of the total sample population. Data collected by Lozoff et al. from 345 Costa Rican infants aged 12-23 months old were used to estimate the parameters of the IDA and NA hemoglobin distributions determined by MDA and the 3-criteria model of iron deficiency. The mean and standard deviation (SD) of the NA hemoglobin distribution determined by both methods was 12.1 +or- 1.0 g/dl. The IDA hemoglobin distribution determined by MDA had a mean and SD of 10.2 +or- 1.3 g/dl, while the IDA distribution by the 3-criteria method had a mean and SD of 10.4 +or- 1.3 g/dl. The prevalences of IDA as estimated by MDA and the 3-criteria method were 24% and 29%, respectively. The sensitivity and specificity of MDA were 95% and 97%, respectively. MDA performed similarly to the 3-criteria method at a simulated high prevalence of IDA and less similar at a low prevalence of IDA.

Unrecognized sexually transmitted infections in rural South African women: a hidden epidemic.

Sexually transmitted infections (STIs) are of major public health concern in developing countries, not least because they facilitate transmission of human immunodeficiency virus (HIV). The present article presents estimates of the prevalence, on any given day, of STIs among women in rural South Africa and the proportion who are asymptomatic, symptomatic but not seeking care, and symptomatic and seeking care. The following data sources from Hlabisa district were used: clinical surveillance for STI syndromes treated in health facilities, microbiological studies among women attending antenatal and family planning clinics, and a community survey. Population census provided denominator data. Adequacy of drug treatment was determined through quality of care surveys. Of 55,974 women aged 15-49 years, a total of 13,943 (24.9%) were infected on any given day with at least one of Trichomonas vaginalis, Neisseria gonorrhoeae, Chlamydia trachomatis, or Treponema pallidum. Of the women investigated, 6697 (48%) were asymptomatic, 6994 (50%) were symptomatic but not seeking care, 238 (1.7%) were symptomatic and would seek care, and 14 (0.3%) were seeking care on that day. Only 9 of the 14 women (65%) were adequately treated. STIs remained untreated because either women were asymptomatic or the symptoms were not recognized and acted upon. Improved case management alone is therefore unlikely to have a major public health impact. Improving partner treatment and women's awareness of symptoms is essential, while the potential of mass STI treatment needs to be explored.

PIP: Estimates of the prevalence, on any given day, of sexually transmitted infections (STIs) among rural South African women and the proportion of these women who are asymptomatic, symptomatic but not seeking care, and symptomatic and seeking care were developed through reference to data from the Hlabisa health district (KwaZulu/Natal). The prevalence of HIV among women attending antenatal clinics in Hlabisa rose from 4.2% in 1992 to 22% in 1997. Data sources included clinical surveillance for STI syndromes treated in health facilities, microbiologic studies among women attending antenatal and family planning clinics, and a community survey. The 1991 population census provided denominator data. It was estimated that, on any given day, 13,943 district women 15-49 years of age were infected with at least one STI--a point prevalence of 24.9% of the resident female population in this age group. Of these women, 6697 (48%) were asymptomatic and 7246 (52%) were symptomatic. Only 252 symptomatic women (2%) sought care and, of these, just 164 (65%) received adequate treatment. The majority of women with an STI were in the 15-29 year age group. Pregnant women were significantly less likely than nonpregnant women to have an asymptomatic infection (1% vs. 59%). Among nonpregnant women, syphilis and Trichomonas vaginalis were more likely to be asymptomatic (67% and 58%, respectively) than infection with Neisseria gonorrhoeae (37%) or Chlamydia trachomatis (36%). These findings indicate that improved STI case management alone is unlikely to improve STI control. Improving women's recognition of and treatment-seeking behavior for abnormal urogenital symptoms should increase the numbers treated, but a large burden of asymptomatic infection will remain unless screening or mass treatment is considered.

Pregnancies averted among U.S. teenagers by the use of contraceptives.

CONTEXT: The personal and social costs associated with teenage pregnancy in the United States concern many policymakers and researchers, yet the role of contraception in preventing these pregnancies has not been adequately quantified. METHODS: Published estimates of contraceptive effectiveness were applied to 1995 National Survey of Family Growth data on sexual and contraceptive practices in order to estimate the number of pregnancies averted through the use of contraceptives by U.S. teenagers. Four scenarios of contraceptives access--from current levels of access to highly restricted access--and teenagers' sexual and contraceptive practices in response to such restrictions are used to project the potential impact on pregnancies among teenagers. RESULTS: Current levels of contraceptive use averted an estimated 1.65 million pregnancies among 15-19-year-old women in the United States during 1995. If these young women had been denied access to both prescription and over-the-counter contraceptive methods, an estimated one million additional pregnancies (ranging from 750,000 to 1.25 million) would have occurred, assuming some decrease in sexual activity. These pregnancies would have led to 480,000 live births, 390,000 abortions, 120,000 miscarriages, 10,000 ectopic pregnancies and 37 maternal deaths. CONCLUSIONS: Contraceptive use by teenage women prevents pregnancies and negative pregnancy-related health consequences that can disrupt the lives of adolescent women and that have substantial societal costs. Continued and expanded access to contraceptives for adolescents is a critically important public health strategy.

PIP: An analysis of the number of adolescent pregnancies and pregnancy outcomes that are averted in the US each year by contraceptive use highlighted the importance of continued and expanded access on the part of young people to contraception. In this analysis, published estimates of contraceptive effectiveness were applied to 1995 National Survey of Family Growth data on sexual and contraceptive practices among US teenagers. Four scenarios of contraceptive access--from current levels to highly restricted access--and sexual and fertility control practices in response to such restrictions were constructed. The 651 sexually active female adolescents enrolled in the national survey had used contraception during 80% of the times in which they were at risk of pregnancy. Current levels of contraceptive use averted an estimated 1.65 million pregnancies among 15- to 19-year-old US women in 1995. If these adolescents had been denied access to prescription and over-the-counter contraceptive methods, an estimated 750,000 to 1.25 million additional pregnancies would have occurred, assuming some decrease in sexual activity. These pregnancies would have resulted in 480,000 live births, 390,000 induced abortions, 120,000 miscarriages, 10,000 ectopic pregnancies, and 37 maternal deaths. The prevalence of adolescent sexual activity would have to decrease by 83% over current levels to avert the same number of pregnancies that are presently prevented by contraceptive use.

Current estimates of and future projections for adult deaths attributed to HIV infection in Zimbabwe.

OBJECTIVE: Estimates of HIV prevalence in 1995 among all adults in Zimbabwe range between about 18% and 24%. The objective of this study was to estimate, for Zimbabwe, the impact of HIV infection on adult mortality, by age and gender, between 1995 and the year 2000. METHODS: For this analysis, we used 1992 census data to estimate the number of non-HIV-related deaths, and a short-term projection model to estimate the number of deaths attributed to HIV infection in 1995 and the year 2000. RESULTS: It was estimated that between 52% and 60% of all adult deaths in 1995 were attributed to HIV infection, and between 69% and 76% in both males and females in the group between 20 and 39 years of age. The estimated adult mortality rate per 1000 increased from 9.8 in 1987 (based on census data) to between 20.6 and 24.3 in 1995. For the year 2000, it was projected that between 66% and 73% of all adult deaths would be attributed to HIV infection, and between 81% and 86% in those aged 20 to 39 years. The estimated adult mortality rate in the year 2000 increased to between 29.1/1000 and 36.6/1000. Even if all transmission was assumed to cease after 1995, it was projected that >60% of adult deaths would be attributed to HIV in the year 2000. Adult population growth is projected to decrease to between 0.3% and 1.0% in the year 2000. CONCLUSION: Results suggest that the impact of HIV infection on mortality in Zimbabwe is already severe and will continue to increase. Efforts to reduce numbers of new HIV infections today will serve to reduce the future burden of mortality, particularly in the longer term.

PIP: Sentinel surveillance surveys for HIV infection have been conducted in Zimbabwe since 1990. Between 1990 and 1995, HIV prevalence among antenatal clinic attendees was 7.7-43.9% in rural areas and 12.3-67.1% in urban areas, with even higher prevalence among STD clinic attendees. As of 1995, an estimated 18-24% of all adults in Zimbabwe were infected with HIV. The authors estimated the impact of HIV infection upon adult mortality in Zimbabwe, by age and gender, between 1995 and 2000. 1992 census data were used to estimate the number of non-HIV-related deaths, while a short-term projection model estimated the number of deaths attributed to HIV infection in 1995 and 2000. An estimated 52-60% of all adult deaths in 1995 were attributed to HIV infection, and 69-76% of all deaths among men and women aged 20-39 years. The estimated adult mortality rate per 1000 increased from 9.8 in 1987 to 20.6-24.3 in 1995. For the year 2000, 66-73% of all adult deaths are projected to be attributed to HIV infection, and 81-86% among people aged 20-39 years. The estimated adult mortality rate in 2000 increased to 29.1-36.6/1000. Even were it assumed that all HIV transmission would cease after 1995, it is projected that more than 60% of adult deaths will be attributed to HIV in 2000, as the rate of adult population growth in that year is projected to decrease to 0.3-1.0%. The already severe impact of HIV infection upon mortality in Zimbabwe will continue to increase.

A methodological strategy for a one-number census in the UK.

"As a result of lessons learnt from the 1991 [U.K.] census, a research programme was set up to seek improvements in census methodology. Underenumeration has been placed top of the agenda in this programme, and every effort is being made to achieve as high a coverage as possible in the 2001 census. In recognition, however, that 100% coverage will never be achieved, the one-number census (ONC) project was established to measure the degree of underenumeration in the 2001 census and, if possible, to adjust fully the outputs from the census for that undercount. A key component of this adjustment process is a census coverage survey (CCS). This paper presents an overview of the ONC project, focusing on the design and analysis methodology for the CCS. It also presents results that allow the reader to evaluate the robustness of this methodology."

How many Californians? A review of population projections for the state.

PIP: This report reviews population projections produced for the state of California by various organizations: California Department of Finance, the US Census Bureau, the US Bureau of Economic Analysis, UCLA, and the Center for Continuing Study of the California Economy. Those population projections are used in short- and long-term planning by local, state, and federal government, and private agencies. The population projection and rates of population growth among these organizations reports that the growth of population in California have been almost equal to that of developing countries though estimations reveal that by the year 2025, the difference between the highest and lowest projection is greater than 10 million people. Even in short terms which is the product of both differing projections of growth and current estimates of the population of the state, significant differences were still noted. By the year 2014, the Census Bureau (CB) estimated that Latinos would constitute the largest race/ethnic group in California, while the dependency ratio would significantly increase by the year 2010. A wide range of current population projection reflects the instability of the demographic future in California. However, these organizations were able to come up with similar observations on the decline of the future growth rate in California compared to the previous rates, with the increase attributed to natural rise of births rather than migration. Policy makers must take into consideration the unstable population in California during program development to ensure that funds are maximized to benefit the whole population.^ieng

Estimating parametric fertility models with open birth interval data.

PIP: This paper demonstrates the approach of extending "date of last birth" (DLB) techniques to parametric models. Estimators for Coale-Trussell M and m parameters are constructed from open interval lengths. A new procedure was applied to Brazilian census data, producing maps and spatial statistics for "births last year" (BLY) and DLB m estimates in 723 municipalities in Minas Gerais. DLB estimators are less sensitive to sampling error than BLY estimators. This increased precision leads to clearer spatial patterns of fertility control, and to improved regression. This study produced two main points. The first is that parametric fertility models may be estimated from open-interval birth data in straightforward fashion. The second point is that use of DLB data can make a critical difference to the quality of statistical results. DLB data are often available to researchers, but they are seldom used to their full potential. When fertility data are collected in last-birth or open-interval form, the methods expounded in this paper can make significant improvements in the demographic analysis of small samples.^ieng

A long period multistate life table using micro data.

PIP: "The multistate life table (MLT) has been widely used by demographers for the past twenty years. However, the pivotal Markov condition upon which the entire methodology rests is rarely satisfied in practice. We lessen reliance upon the assumption by computing transition probabilities for longer periods of time than was previously practical. An extended Kaplan-Meier estimator accomplishes this task, simultaneously addressing the issue of censoring.... We provide an illustrative example of a 10-year period MLT, with comparison to a 1-year period MLT." The data for California are used as an illustration. (EXCERPT)^ieng

The long-term pattern of adult mortality and the highest attained age.

"Recent new data on old age mortality point to a particular model for the way in which the probability of dying increases with age. The model is found to fit not only modern data but also some widely spaced historical data for the 19th and 17th centuries, and even some estimates for the early mediaeval period. The results show a pattern which calls for explanation. The model can also be used to predict a probability distribution for the highest age which will be attained in given circumstances. The results are relevant to the current debate about whether there is a fixed upper limit to the length of human life." A discussion of the paper by several researchers and a reply by the author are included.

[Demographic perspectives]. / Perspectives demographiques.

PIP: This is a brief review of possible future developments in global population trends. The author notes that the world's population will number between 8 and 11 billion by the year 2050. Topics discussed include changes in the regional balance of population, changes in the age composition of the population, and demographic aging in Europe.^ieng

Do immigrants working illegally reduce the natives' legal employment? Evidence from Italy.

PIP: This paper examines how immigrants working illegally in the shadow economy affect the legal employment of native and foreign workers in the official economy of Italy. The data set used was provided by the Central Statistical Office and includes information regarding the units of labor employed both in official production and in underground production; employment in the latter is subdivided into native workers and foreign workers. Estimates were then made as to how "legal employment" has reacted to changes in "illegal employment", with special reference to the effect of the foreign component of "illegal labor". The results of the cross sector-time series analysis of the demand for legal labor in the Italian economy from 1980 to 1995 showed that the increase of illegal units of labor produces a reduction in the use of legal labor, albeit a very limited one. An analysis by sectors shows that the competitive effects of illegal foreign workers is not homogeneous and is strongest in the agricultural sector while complementarity between the two categories of labor is evident in the nontradable services sector. When comparing the number of effects of illegal foreign and illegal native workers, illegal native workers are lower than the illegal foreign workers. Despite regularization in Italy and the lack of flexibility in the labor market, neither regular nor nonregular foreign workers have begun to openly displace native workers.^ieng

Population forecasting with endogenous migration: an application to trans-Tasman migration.

"This article focuses on forecasting migration between Australia and New Zealand (trans-Tasman migration), which is largely visa-free and therefore resembles internal migration. Net trans-Tasman migration is a major component of New Zealand population change and is embedded in this article in a Bayesian or unrestricted vector autoregression (VAR) model, which includes foreign and domestic economic variables. When time series of net migration are available, this approach provides a useful input into forecasting population growth in the short run in the absence of major policy changes. This conclusion applies equally to interregional migration and to unrestricted international migration between economically integrated nations."

Estimating the regional migration patterns of the foreign-born population in the United States: 1950-1990.

PIP: "In this paper, we apply model schedules to graduate data on the internal and external regional [U.S.] migration patterns of the foreign-born population for the 1950-1990 period.... To find estimates of the unrecorded migration flows in-between for four census-defined periods in our study (that is, for 1950-1955, 1960-1965, 1970-1975, and 1980-1985) we interpolate between the data of adjacent census time periods. Finally, we combine the estimated migration data with the corresponding mortality data to calculate and analyze the multiregional life tables and projections associated with each five-year time interval." (EXCERPT)^ieng

Modeling approaches to the indirect estimation of migration flows: from entropy to EM.

PIP: "The paper presents probability models to recover information on migration flows from incomplete data. Models are used to predict migration and to combine data from different sources.... Two models are considered: the binomial (multinomial) model, which underlies the logit model and the logistic regression, and the Poisson model, which underlies the loglinear model, the log-rate model and the Poisson regression.... By way of illustration, the probabilistic approach and the EM algorithm are applied to two different missing data problems." (EXCERPT)^ieng

Assessing structural change in U.S. migration patterns: a log-rate modeling approach.

PIP: "A set of log-rate models is proposed to transform Rogers and Wilson's accounting-based migration models into statistics-oriented migration models. This study demonstrates not only how log-rate models can be used to replicate results generated from Rogers-Wilson's cohort and multi-region mobility models, but also how log-rate models can be used to make statistical inferences and to derive more parsimonious models. Estimation issues and model fit are discussed, and case studies with U.S. mobility and interregional migration data are provided. The flexibility of log-rate models is emphasized, and possible uses for such models, such as the testing of various hypotheses and migration projection, are explored. Potential applications and limitations of log-rate models are also discussed." (EXCERPT)^ieng