[Legalization and dissolution of consensual unions: an example of log-linear models used to estimate models of competing risk]. / Legalizacion y disolucion de uniones consensuales: un ejemplo del uso de modelos log-lineales para estimar modelos de riesgos en competencia.

PIP: "This is a mainly methodological work: a generalization of the so-called proportional risk models to cases of multiple and competing risks.... Proportional risk models are an extension of the methodology implied in calculating mortality tables, where the risk function is made to depend on some variables (covariables), as in a regression model.... Life-table methodology has been...an essential instrument in demographic calculus and analysis." The author uses the proposed methods to analyze the determinants of the legalization and dissolution of consensual unions in Mexico. (EXCERPT)^ieng

Decline of tuberculosis mortality in an urban Mexican-origin population, 1935-1984.

Through a series of life table analyses, this paper describes the natural history of tuberculosis mortality in a Mexican-origin community over five decades (1935-84) during which the disease underwent a transition from a major underlying cause of death to a disease conditioned mentioned more often on death certificates as contributing to death than causing death. The decline in death rates from 1940 to 1950 was especially remarkable. Successive birth cohorts of Mexican Americans, separated by as little as five years of age, experienced distinctly lower risk of death from tuberculosis as they entered young adulthood. There was a rapid convergence in age-specific patterns of tuberculosis death rates in Mexican Americans toward those of non-Hispanic whites, so that by 1960 tuberculosis was primarily a cause of death in old age rather than young adulthood. The impact of changing environment, both through improvements of conditions within neighborhoods and through residential mobility, on birth cohorts at risk of tuberculosis needs to be examined in further research.

PIP: This study examines the history of tuberculosis mortality during 1935-84 among a Mexican-origin community in Bexar County, Texas. Data were obtained from death records of the San Antonio Metropolitan Health District. Data coding accounted for the shift in 1949 in formatting underlying cause and primary cause of death. Deaths are estimated from multiple decrement life tables for deaths by age and underlying cause in a hypothetical cohort of 100,000 newborns followed to their deaths. Cause-eliminated life tables show the distributions of deaths if tuberculosis were eliminated. Findings indicate that life expectancy of Mexican-origin people in Bexar County during 1938-42 was about 47 years for males and females. Life expectancy for Anglos was higher but still lower than the national average. By 1980, differences in life expectancies by ethnic group converged. The rapid increases in life expectancy occurred during the 1940s: 12.7 years for Mexican-origin women and 10.3 years for Mexican-origin men. The 1940 risk of tuberculosis death among Mexican-origin people was 5-7 times that of Anglos. Among the 1940s Mexican-origin population, tuberculosis caused heavy fatalities in early adulthood between the ages of 15 and 35 years. By 1960, it was a cause only in old age, as it was among Anglos. Cohort comparisons reveal that the cohort reaching the age of 15 years in 1945 had a mortality probability that was only half as great to age 20 in 1950. The mortality probability declined to near zero by age 25 in 1955. The life table proportion of deaths due to tuberculosis declined linearly and added to life expectancy until 1980. Tuberculosis was the underlying cause of death among 96% of Mexican-origin people in 1938-42 and 41% in 1983-85. Tuberculosis morbidity declined during the 1940s and 1950s due to major housing renewal, slum clearance, code enforcement, and residential mobility.

Brazil: model life tables and stable population.

"In the 1974 Meeting of the Brazilian Association for Population Studies, Frias and Leite presented a set of model life tables that were meant to reflect the sex-age structure of Brazilian mortality. A later examination of this study revealed the need for revision and further development in order to improve this valid piece of work." The present article reviews and complements the earlier study.

[Model representation of mortality patterns]. / Representacao de modelos padroes de mortalidade.

PIP: "In this study a bibliographic review of the classical model life tables in the demographic literature is done, calling...attention to the characteristics and limitations of using such models for constructing complete life tables. A critical review with relation to the ¿Brazil Model' of life tables [is done] and two new models [are] proposed based on the Brazilian experience of mortality." (EXCERPT)^ieng

An alternative procedure for fitting relational model life tables.

"The paper considers the problem of fitting a relational model life table to mortality data which does not include reliable estimates of infant and child mortality. This type of data could arise from indirect estimation of adult mortality using orphanhood or widowhood, or from adjustment of incomplete registration data using growth balance methods in a population recently de-stabilized by falls in fertility. The proposed fitting technique can give equal weight to all the age specific mortality risk information available, rather than giving more weight to the information for younger ages, as is the case with the traditional method. An application to Brazilian data is presented." (SUMMARY IN ITA AND FRE)

The marriage squeeze and the rise in informal marriage in Brazil.

Around the world, populations have experienced shortages of one sex or the other at marriageable ages, as a result of mortality declines. The solutions to this problem vary with the cultural context. Declines in the spousal age difference and increases in dowry payments (India) and polygamy (Africa) are two adjustments to a disequilibrium in the marriage market. We hypothesize that in Brazil the marriage market finds its balance by "recycling" men through highly unstable informal unions. Using census and 1984 survey data, we establish the relationship between a marriage squeeze and the increase in informal marriage. Census data and a competing-risks analysis of marriage choice provide evidence that a marriage squeeze has affected both the chances of marrying at all and the type of marriage entered.

PIP: The competing risks logistic model of the likelihood of entering a formal or informal union or staying single in Brazil reveals that race has a strong effect on marriage choice and marriage, only when region of residence is not included in the model. Blacks are more likely than Whites to enter informal unions. Asians are less likely to enter informal unions. Women in the northeast are less likely to enter formal marriages and more likely to enter informal unions than remaining single. Women in the south are more likely to enter formal marriages. Chances of entering an informal union are increased with urban residence and younger age. Increased schooling decreases the likelihood of entering a formal or informal union. Higher unearned income increases the likelihood of entering an informal union. After age 25 age becomes important in influencing the effects on entering informal and formal unions. Women over the age of 25 years and under the age of 35-39 years are less likely to enter formal unions and more likely to enter informal unions. Women over the age of 35-39 years are less likely to enter informal unions. The proportion of women working decreases the likelihood of formal marriage compared to remaining single and increases the likelihood of consensual unions. A greater supply of men increases the chances of entering a formal marriage rather than remaining single. The supply of men has no effect on remaining single compared to entering an informal union. Census data for 1980 on state level sex ratios and rates of divorced males per ever married women reveal that as the pool of marriageable men declines, it is easier for women to marry, stay married, and to remarry. It is more difficult for men to do so. The interpretation of findings is that Brazil's solution to the marriage squeeze is the recycling of marriage partners and an increase in informal unions. Other non-Latin countries exhibit different responses to the marriage squeeze, such as increased rates of polygyny or reduced spousal age differences.

Effectiveness of the diaphragm, used continuously, without spermicide.

The experience of 670 diaphragm users from three Brazilian clinics was retrospectively reviewed. Most of the subjects (441) followed the traditional method (TM) of using the diaphragm, only at the time of sexual intercourse and with spermicide. One third (215) used the diaphragm continuously (CU), without spermicide, removing it only at the time of their daily shower to wash it, with immediate re-insertion. The total pregnancy rate was 7.0 per 100 women-years for the whole group. Patient and total failure rate were significantly lower in the CU (0.6 and 2.8), in comparison with the TM sub-group (6.5 and 9.8). The discontinuation rate for urinary infection or other medical reasons was not greater in the CU group. Logistic regression analysis, including age, parity, number of abortions and of living children, years of schooling, whether living with a partner, presence of mild cystocele or retroverted uterus, and form of use of diaphragm (TM or CU), showed that only the TM of diaphragm use was positively associated to patients' and total failure rate.

PIP: In Brazil, a retrospective review of clinical records of diaphragm users from the Sexuality and Health Women's Collective in central Sao Paulo, the family planning clinic at the State University of Campinas, and a private practice in Belo Horizonte was performed to compare data on 215 women continuously using it without spermicide, except to clean it during a shower, with data on 441 women using it with spermicide only during sexual intercourse to determine diaphragm effectiveness. The patients' failure rate stood considerably higher among women using the diaphragm with spermicide (6.5 vs. 0.61; p .05). The method failure rate was just slightly higher in the diaphragm with spermicide users' group (3.53 vs. 2.2). 71.47% of all women continued use for 12 months, especially women continuously using the diaphragm without spermicide (84.84 vs. 63.28%; p .05). Women who used the diaphragm with spermicide were more likely to discontinue for vaginal discharge and for other medical and personal reasons than were those who continuously used it without spermicide (p .05). They were also more likely to be lost to follow up (16.4% vs. 6.43%; p .05). The logistic regression analysis indicated that diaphragm with spermicide use was positively linked to patients' and total failure (p = .042). These findings suggested that the messiness of diaphragm use with spermicide, its interference with sexual intercourse, and perhaps spermicide cost contributed to its high discontinuation and failure rates. The findings should raise interest in identifying means to improve acceptance of and use effectiveness of the diaphragm.

The dynamics of contraceptive use in Peru.

In 1986, the Demographic and Health Surveys project administered the first six-year calendar history of events that included women's contraceptive use and their reasons for discontinuation in experimental surveys in Peru and the Dominican Republic. In this report the experimental survey from Peru is examined to demonstrate how the calendar data can be used to calculate multiple increment-decrement life table rates of contraceptive discontinuation--including contraceptive failure, method switching, and abandonment of use--and of resumption of method use following discontinuation. These analyses reveal that nearly half of all Peruvian women who begin to use a method will stop using it within one year; 29 percent of women discontinue method use for nonpregnancy-related reasons within one year of initiating use. Women who switch methods do so frequently, and many will return to a method used previously, or move on to a third method. Women who become pregnant after abandoning contraceptive use have similar contraceptive-use patterns to women who experience a contraceptive failure.

PIP: An analysis of calendar data from January 1981 to interview date in 1986 (Demographic and Health Survey) on 1065 ever married Peruvian women who had ever used a contraceptive was used to show how researcher can use these data to calculate multiple increment-decrement life table rates of contraceptive discontinuation and renewed method use after discontinuation. 46.4% of women discontinued a method within 1 year. 29% discontinued a method for nonpregnancy related reasons within 1 year of use. Women who stopped using a method were more likely to switch directly to another method than not use any method. The risk of unplanned pregnancy was therefore low for these women. Women who discontinued use of a method but not switch directly to another method likely ceased having sexual intercourse, while others either ran out of supplies, were dissatisfied with the method, or could not find acceptable alternative methods. Regardless of the reason for not switching to another method after discontinuation, these women were at an increased risk of unplanned pregnancy. Women who discontinued a method and did not directly switch to another method were just as likely to return to the abandoned method as they were to switch to another method, but were likely to become pregnant before they returned to the abandoned method or switched to another method. Contraceptive use patterns of such pregnant women matched those of women whose contraceptives failed. Both groups of women tended to return to the method that failed. The considerable amount of method switching in a population may demonstrate either that women profit from a wide range of contraceptive choices or they cannot easily obtain and are not satisfied with currently available contraceptives. Since Peru had one of the weakest family planning programs in Latin America during the 1980s, the latter 2 reasons were most likely the case.

A comparison of the fertility of Dominican, Puerto Rican and mainland Puerto Rican adolescents.

Data from three fertility surveys are used to examined the probabilities and determinants of adolescent births among Dominican and Puerto Rican women. Young women in the Dominican Republic are the most likely to have had a child by each year of age from 14 through 24, followed by young women on the Island of Puerto Rico; the probability of an early birth is lowest for Puerto Rican women on the U.S. mainland. Eighteen percent of Dominican women have had a child before their 18th birthday, compared with 13% of women living in Puerto Rico, and 10% of Puerto Rican women in metropolitan New York. The cumulative probabilities that Puerto Rican women will have borne a child before their 20th birthday are almost identical, whether the women live on the island or the U.S. mainland, but the difference between Puerto Rican and Dominican women widens. The order is reversed, however, in the analysis of premarital births: The probability of a premarital birth during adolescence is highest for Puerto Rican women in New York, and lowest for Dominican women. In a separate logistic regression analysis, education and age at first sexual intercourse are shown to be important determinants of adolescent fertility in all three populations.

PIP: Researchers analyzed 1980s data on female adolescents including Puerto Ricans in the New York metropolitan area, those in Puerto Rico, and Dominicans in the Dominican Republic to determine the probabilities and determinants of adolescent births among these women. Female adolescents from the Dominican Republic had the highest probability of having delivered an infant by each year from 14-24 years followed by those in Puerto Rico and then Puerto Rican immigrants in the US. For example, the cumulative hazard rate at age 24 was .65 for the Dominicans compared to 0.5 for Puerto Ricans in Puerto Rico and in the US. Moreover 18% of Dominicans delivered an infant before 18 years old whereas this figure for the 2 Puerto Rican groups was 13% and 10% respectively. Further the cumulative probabilities that Puerto Rican female adolescents will have had a child before 20 years old were essentially equal (37.4% and 37.3% respectively) compared to 56.1% for the Dominicans. On the other hand, the order was opposite for premarital births. Puerto Rican women living in metropolitan New York were at greatest risk of having a premarital birth (cumulative hazard rate at age 24=.2) then those living in Puerto Rico (.1) followed by Dominican women (.05). Age at 1st intercourse was the strongest determinant of adolescent birth in all 3 countries (p=.001). Indeed the younger the adolescent was at 1st intercourse, the greater the likelihood she would deliver a child while an adolescent. Another strong determinant of adolescent birth was dropping out of school (p=.001 in US and Puerto Rico; p=.01 in the Dominican Republic). The fact that most women did not use contraceptives before 1st birth was only significant for the women not living in the US (p=.001). Further research is needed to identify regional and cohort differences in contraceptive use and attitudes toward early sexual activity and childbearing.

Worldwide variations in the lifetime probability of reproductive cancer in women: implications of best-case, worst-case, and likely-case assumptions about the effect of oral contraceptive use.

Cancer incidence in countries representative of three patterns of reproductive cancer and age-specific mortality was used to estimate the effect of oral contraceptive use on the lifetime probability of reproductive cancer under three sets of assumptions about the effects of oral contraceptives. Under the set of assumptions considered likely, oral contraceptives were estimated to reduce or increase only slightly the lifetime probability of any reproductive cancer in each setting. Under worst-case assumptions, oral contraceptives were estimated to increase the lifetime probability of reproductive cancer only modestly in settings with low cancer rates and in settings with high rates of breast, ovarian, and endometrial cancer, but it might have a large impact on lifetime probability of reproductive cancer in settings with high cervical cancer rates. Under best-case assumptions, oral contraceptives were estimated to decrease the lifetime probability of reproductive cancer in each setting; this reduction was estimated to be greatest in settings where endometrial and ovarian cancer incidence are high.

PIP: Researchers applied published data on cancer incidence and age specific mortality to standard life table techniques to estimate the lifetime probability of developing reproductive cancer for women living in countries representative of 3 patters of risk of reproductive cancer and for long term oral contraceptives (OC) users under best case, worst case, and likely case assumptions. The reproductive cancers included breast, ovarian, endometrial, and cervical cancers. The data consisted of urban women from China, Japan, United States (California), England, Wales, Costa Rica, and Colombia. Under the likely case assumption, OCs just barely reduced or increased the lifetime probability of any reproductive cancer in any setting. Further, under the worst case scenario, OCs increased the lifetime probability or reproductive cancer moderately in countries with low cancer rates (Asian countries) and in countries with high rates of breast, ovarian, and endometrial cancer (Western Europe, North America, and Australia). Yet in countries with high cervical rates (South and Central America), OC use significantly affected the lifetime probability of reproductive cancer. The best case scenario revealed that OCs decreased lifetime probability of reproductive cancer in each country, especially those countries where endometrial and ovarian cancer incidences were great. The analysis also showed that OC use has the greatest effect on lifetime probability of reproductive cancer, be it positive or negative, in countries with high underlying rates of reproductive cancer. Further it demonstrated that the effect of OC use will most likely be small in countries with low incidence of reproductive cancers. Overall the researchers felt reassured about OC use and reproductive cancer. Even though long term OC use increases the risk of breast cancer in young ages.

A simplified methodology for the community-based assessment of breast-feeding and amenorrhoea in Mexico.

Reported is the use of a simplified methodology for carrying out a community-based epidemiological assessment that is compatible with the goals of primary health care research. For this purpose, a current-status life table analysis of data from 1131 women who were served by community health workers in the State of México was used to determine the distributions of the duration of postpartum breast-feeding, amenorrhoea, and contraceptive use. The field methods used incorporated quality assurance procedures. At 1 month postpartum, 78% of the infants were still being breast-fed, at 5 months 50%, and at 12 months 25%. The level of amenorrhoea at 1 month postpartum was 85%, at 3 months 50%, and at 5 months 25%. Use of contraceptives was initiated at an early stage, with 42% of all users beginning during the first month postpartum. The simplified method described permitted the area's primary health care administrators to carry out research projects for programme development rapidly and was compatible with the locally available resources.

PIP: Reported here is the use of a simplified methodology for carrying out a community-based epidemiological assessment that is compatible with the goals of primary health care research. For this purpose, a current status life table analysis of data from 1131 women who were served by community healthworkers in the state of Mexico was used to determine the distributions of the duration of postpartum breastfeeding, amenorrhea, and contraceptive use. The field methods used incorporated quality assurance procedures. At 1 month postpartum, 78% of the infants were still being breastfed, at 5 months 50%, and at 12 months 25%. The level of amenorrhea at 1 month postpartum was 85%, at 3 months 50%, and at 5 months 25%. Use of contraceptives was initiated at an early stage, with 42% of all users beginning during the 1st month postpartum. The simplified method described permitted the area's primary health care administrators to carry out research projects for program development rapidly and was compatible with the locally available resources. (author's)

[Mortality in the 1980s]. / La mortalidad en los anos ochenta.

PIP: The author analyzes mortality levels in Mexico by age and sex according to selected socioeconomic and geographic variables for the period 1980-1985. Mortality in 1980 is first reviewed. Complete life tables are then provided for 1983-1985 for the whole country. Male mortality showed the greatest decline, due to a decrease in deaths from violence and accidents.^ieng

Mini-pill in lactating women.

A non-comparative study of the progestogen-only oral contraceptive, norgestrel 0.075 mg, in breast-feeding women was conducted at the Centro de Investigaciones Regionales, Merida, Yucatan, Mexico. The study was designed to evaluate the overall acceptability and contraceptive efficacy of norgestrel in breast-feeding women. This report includes a survey of 200 women, all of whom were less than 26 weeks postpartum at admission; 113 were interval patients and 87 were postpartum. Follow-up visits were scheduled at 2, 6 and 12 months after admission. Overall, women experienced an increase in intermenstrual bleeding, amenorrhea, vaginal discharge and breast discomfort. The discontinuation rate at 12 months was 32.5 and the corresponding lost to follow-up rate was 22.5; this is a measure of acceptability. The 12-month life-table rate for pregnancy was 3.4 with a standard error of 2.0. Three women discontinued use of the mini-pill due to accidental pregnancy. One pregnancy was attributed to user failure and the woman conceived 9 months after entering into the study; the other two were attributed to method failure, one woman conceived 3 months after admission and the other conceived 6 months after admission.

A comparative clinical trial of Norinyl 1/35 versus Brevicon in Rio Clara, Brazil.

A comparative clinical trial of two combined oral contraceptives (OCs) with equivalent estrogen content, but different amounts of progestogens, was conducted at the Centro Medico Especializado em Planejamento Familiar in Rio Clara, Brazil. The study was designed to determine the differences in discontinuation rates between Norinyl 1/35 (Syntex) and Brevicon (Syntex) as well as the frequency of selected side effects which might contribute to method discontinuation. Both OCs contain 0.035 mg of ethinyl estradiol; Brevicon contains 0.5 mg and Norinyl 1/35 contains 1 mg norethindrone. Three-hundred women enrolled in the study were randomly assigned to either the Norinyl 1/35 or Brevicon OCs and follow-up visits were scheduled at 1, 4, 8 and 12 months after admission. Intermenstrual bleeding was reported by significantly more women in the Brevicon group than in the Norinyl group (p less than 0.05), and significantly more Brevicon users reported an increase in intermenstrual bleeding. At the end of the study period, no differences were found between the two OC groups in terms of discontinuation rates, but a large number of women in each group discontinued for menstrual problems. The total discontinuation rates at 11 months for both groups were extremely high: 68.2 for the Norinyl 1/35 group and 75.2 for the Brevicon users. The largest group of discontinuations were comprised of those discontinuing for menstrual problems, other personal reasons, planned pregnancy and side effects.

Analysis of sterilization failure in Brazil.

A study of 13,423 female sterilization procedures performed from 1981 to 1984 in Rio de Janeiro, Brazil, was conducted to determine the level of sterilization failure. The lifetable cumulative failure rate was 0.54 at 12 months per 100 initial sterilizations, increasing to 1.04 at 48 months. Results of a multivariate analysis indicated that the differential in the rate of sterilization failure by woman's age at sterilization at 12 and 24 months was statistically highly significant. However, the differential rate of failure by the other variables such as whether sterilized during a training period, number of sterilizations per surgeon per day, and year of sterilization were not statistically significant.

PIP: To determine the level of sterilization failure, an analysis of the 13,423 female sterilization procedures carried out in 1981-84 at a primary care center in Rio de Janeiro was performed. 97% of these procedures were performed with a laparoscope, and a band was used for 98% of occlusions. 144 women reported a pregnancy after their sterilization procedure; of these, 22 were defined as occurring before the surgery (luteal phase) and were excluded from the life-table analysis. The cumulative failure rate was 0.54/100 sterilizations at 12 months and 1.04/100 procedures at 48 months. Parity, method of sterilization, and occlusion technique were not correlated with sterilization outcome. However, logistic regression analysis indicated that the rates of sterilization failure at 12 and 24 months were consistently lower for older women (age 30 years and above) than women in the 17-29-year age group. (p0.01). The number of sterilizations performed per day was also a factor in sterilization failure, but this association was not statistically significant. 5.7% of the sterilization failures resulted in ectopic pregnancies. Overall, these findings are comparable to the failure rate in other countries. The occurrence of 22 luteal phase pregnancies in this study highlights the importance of thorough preoperative counseling and examination. It is recommended that contraception should be used in the cycle prior to sterilization to reduce this risk.

Seminar on adult mortality and orphanhood in the past: five Latin American cases.

This report concerns a seminar on adult mortality and orphanhood in the past in Latin America that was held in San Jose, Costa Rica, December 12-14, 1984. The first part describes five historical studies presented at the seminar concerning Mexico, Chile, Peru, Brazil, and Argentina. "The second part of this article is an explanation of the calculation involved in a life table derived from information on the incidence of orphanhood according to the age of newly married couples on their marriage."

[Orphans and adult mortality. The example of France between 1740 and 1829]. / Los huerfanos y la mortalidad adulta. El ejemplo de Francia de 1740 a 1829.

The relationship between adult mortality and the proportion of orphans in France in the eighteenth and nineteenth centuries is analyzed. Data are from a research project developed at the Institut National d'Etudes Demographiques [INED] and concern data for some 400 communes, together with life tables developed for the periods 1740-1749 and 1820-1829. "This paper is divided in two chapters. The first chapter examines the different proportions of orphans, observed in the above mentioned periods. The second one confronts these proportions with comparable values derived from mortality tables." Consideration is given to the relationship between parents' death and timing of marriage of

[Adult mortality and orphanhood in the past: five Latin American cases]. / Mortalidad adulta y orfandad en el pasado: cinco casos latinoamericanos

"This paper describes the historical evolution of five populations and analyzes the circumstances under which data on maternal and paternal orphanhood of couples at the moment of marriage were collected and compiled." The data, which concern historical populations in Mexico, Chile, Peru, Brazil, and Argentina, are used to construct life tables for male and female adults. Consideration is given to mortality differentials by sex. (summary in ENG)

[Estimation of adult mortality in six parishes of the central valley of Costa Rica (1888-1910) based on information on orphanhood]. / Estimacion de la mortalidad adulta en seis parroquias del valle central de Costa Rica (1888-1910) a partir de la informacion sobre orfandad

"This paper contains an application of the orphanhood method for estimating adult mortality, based on information provided during the period 1888-1910 by the brides and bridegrooms of six parishes of the Central Valley of Costa Rica.... Using the Brass technique for estimating adult mortality from orphanhood and interpolating the resulting probabilities of surviving into... Coale and Demeny's regional model life tables, the life expectancy at the age of 25 years is estimated [at] 41 years for women and 40 years for men." Mortality differences by region and social-occupational group are considered. (summary in ENG)

[Abbreviated life tables prepared at CELADE, San Jose, to be used in population projections]. / Tablas limite de mortalidad preparadas en CELADE San Jose para su uso en proyecciones de poblacion

PIP: Some problems related to the use of abbreviated life tables to project mortality by age in Latin America are discussed. The life tables previously used, which were developed by Jean Bourgeois-Pichat in 1952, are shown to produce exaggerated male excess mortality in the first years of life. The new series of abbreviated life tables developed at CELADE in San Jose, Costa Rica, to overcome this problem is described. (summary in ENG)^ieng