Long-term population projections: Scenarios of low or rebounding fertility.

The size of the human population is projected to peak in the 21st century. But quantitative projections past 2100 are rare, and none quantify the possibility of a rebound from low fertility to replacement-level fertility. Moreover, the most recent long-term deterministic projections were published a decade ago; since then there has been further global fertility decline. Here we provide updated long-term cohort-component population projections and extend the set of scenarios in the literature to include scenarios in which future fertility (a) stays below replacement or (b) recovers and increases. We also characterize old-age dependency ratios. We show that any stable, long-run size of the world population would persistently depend on when an increase towards replacement fertility begins. Without such an increase, the 400-year span when more than 2 billion people were alive would be a brief spike in history. Indeed, four-fifths of all births-past, present, and future-would have already happened.

Near-universal marriage, early childbearing, and low fertility: India's alternative fertility transition.

OBJECTIVE: To compare fertility in India to both low-to-middle-income and high-income countries (LMICs and HICs) and describe the patterns that have accompanied India's transition to low fertility. METHODS: We use data from the Demographic and Health Surveys (DHS), the United Nations (UN), and the Organisation for Economic Co-operation and Development (OECD) to observe factors associated with fertility decline in 36 Indian states and 76 countries. RESULTS: Although fertility in India has declined to levels similar to HICs, women's entry into marriage and initiation of childbearing are more in line with patterns found in LMICs. The vast majority of women in India (97%) are married by age 30, and their average age at first birth is only 21.3 years old. In spite of these patterns, average fertility has declined in India as a result of earlier termination of childbearing. Among more recent cohorts, fewer women progressed to higher-order births and about half of women obtained a sterilization by age 35. CONCLUSIONS: India has reached low fertility by mechanisms outside the traditional indicators of fertility decline. In contrast to countries that have achieved low fertility through delayed age at first birth, women in India have continued to enter unions and bear children early, lowered their age at last birth, and increasingly ended their fertility via sterilization following the birth of two children. CONTRIBUTION: Evidence from India reveals an alternative pathway to low fertility, highlighting the limitations of traditional socioeconomic indicators for explaining fertility decline.

Research Note: Intergenerational Transmission Is Not Sufficient for Positive Long-Term Population Growth.

All leading long-term global population projections agree on continuing fertility decline, resulting in a rate of population size growth that will continue to decline toward zero and would eventually turn negative. However, scholarly and popular arguments have suggested that because fertility transmits intergenerationally (i.e., higher fertility parents tend to have higher fertility children) and is heterogeneous within a population, long-term population growth must eventually be positive, as high-fertility groups come to dominate the population. In this research note, we show that intergenerational transmission of fertility is not sufficient for positive long-term population growth, for empirical and theoretical reasons. First, because transmission is imperfect, the combination of transmission rates and fertility rates may be quantitatively insufficient for long-term population growth: higher fertility parents may nevertheless produce too few children who retain higher fertility preferences. Second, today even higher fertility subpopulations show declining fertility rates, which may eventually fall below replacement (and in some populations already are). Therefore, although different models of fertility transmission across generations reach different conclusions, depopulation is likely under any model if, in the future, even higher fertility subpopulations prefer and achieve below-replacement fertility. These results highlight the plausibility of long-term global depopulation and the importance of understanding the possible consequences of depopulation.

Social disadvantage, economic inequality, and life expectancy in nine Indian states.

SignificanceIndia is one of the most hierarchical societies in the world. Because vital statistics are incomplete, mortality disparities are not quantified. Using survey data on more than 20 million individuals from nine Indian states representing about half of India's population, we estimate and decompose life expectancy differences between higher-caste Hindus, comprising other backward classes and high castes, and three marginalized social groups: Adivasis (indigenous peoples), Dalits (oppressed castes), and Muslims. The three marginalized groups experience large disadvantages in life expectancy at birth relative to higher-caste Hindus. Economic status explains less than half of these gaps. These large disparities underscore parallels between diverse systems of discrimination akin to racism. They highlight the global significance of addressing social inequality in India.

Gender and LPG use after government intervention in rural north India.

Exposure to air pollution from cooking with solid fuels has important consequences for public health. This paper focuses on rural north India, where despite robust economic growth and government subsidies, the vast majority of households mainly use solid fuels. We draw on new qualitative and quantitative data collected in the context of a policy environment that dramatically expanded ownership of liquid petroleum gas (LPG) to examine why households are slow to adopt clean fuels in rural north India. We find that patriarchal gender norms and attitudes encourage the use of solid fuels in this region. North Indian society confers low status to women, promotes women's seclusion, and constrains women's engagement in economic activities outside of the home. These beliefs encourage women to preserve gas, promote women's work that facilitates the use of solid fuels, and hinder communication between the cook and the decision-maker regarding LPG refills. When rural north Indian households use gas, it is frequently to facilitate the adherence to norms of seclusion that prevent women from leaving the home to collect solid fuels. In addition to expanding access and improving economic conditions, future research and policy interventions should pay careful attention to the gender norms and attitudes that discourage the use of gas. Addressing these beliefs and norms is essential to sustained LPG use and health improvements.

Revisiting Open Defecation: Evidence from a Panel Survey in Rural North India, 2014-18.

Since October 2014, the Government of India has worked towards the goal of eliminating open defecation by 2019 through the Swachh Bharat Mission. Since October 2014, the Government of India (GOI) has worked towards the goal of eliminating open defecation by 2019 through the Swachh Bharat Mission (SBM). In 2014, several of the co-authors reported on a survey of rural sanitation behaviour in North India (Coffey et al 2014) conducted by the Research Institute for Compassionate Economics (r.i.c.e.). Different statistical methods produce slightly different numbers, but results from a wide range of approaches used concur that approximately 40% to 50% of rural people in these states defecated in the open in late 2018. The 2014 survey used a multistage sampling strategy to select households: first, districts were purposively selected to match the state-level trend in rural open defecation between the 2001 and 2011 Censuses; second, villages were randomly drawn using proportional-to-size sampling from a frame taken from the Government of India's District Level Health Survey; third, households were selected using an in-field randomisation technique similar to that used for Pratham's Annual Status of Education Report (ASER) survey.

Persistence of Solid Fuel Use in Rural North India.

Survey evidence from rural North India showing persistent solid fuel use despite increases in liquefied petroleum gas ownership is presented. Although three-quarters of survey households in these states had LPG, almost all also had a stove that uses solid fuels. Among those owning both, almost three-quarters used solid fuels the day before the survey. Household economic status, relative costs of cooking fuels, gender inequality, and beliefs about solid fuels were important contributors to high solid fuel use. To realise the full health benefits of the LPG expansion, attention must now be turned towards encouraging exclusive LPG use.

Measuring open defecation in India using survey questions: evidence from a randomised survey experiment.

OBJECTIVES: To investigate differences in reported open defecation between a question about latrine use or open defecation for every household member and a household-level question. SETTING: Rural India is home to most of the world's open defecation. India's Demographic and Health Survey (DHS) 2015-2016 estimates that 54% of households in rural India defecate in the open. This measure is based on a question asking about the behaviour of all household members in one question. Yet, studies in rural India find substantial open defecation among individuals living in households with latrines, suggesting that household-level questions underestimate true open defecation. PARTICIPANTS: In 2018, we randomly assigned latrine-owning households in rural parts of four Indian states to receive one of two survey modules measuring sanitation behaviour. 1215 households were asked about latrine use or open defecation individually for every household member. 1216 households were asked the household-level question used in India's DHS: what type of facility do members of the household usually use? RESULTS: We compare reported open defecation between households asked the individual-level questions and those asked the household-level question. Using two methods for comparing open defecation by question type, the individual-level question found 20-21 (95% CI 16 to 25 for both estimates) percentage points more open defecation than the household-level question, among all households, and 28-29 (95% CI 22 to 35 for both estimates) percentage points more open defecation among households that received assistance to construct their latrines. CONCLUSIONS: We provide the first evidence that individual-level questions find more open defecation than household-level questions. Because reducing open defecation in India is essential to meeting the Sustainable Development Goals, and exposure to open defecation has consequences for child mortality and development, it is essential to accurately monitor its progress. TRIAL REGISTRATION NUMBER: Registry for International Development Impact Evaluations (5b55458ca54d1).

The association of early-life exposure to ambient PM2.5 and later-childhood height-for-age in India: an observational study.

BACKGROUND: Children in India are exposed to high levels of ambient fine particulate matter (PM2.5). However, population-level evidence of associations with adverse health outcomes from within the country is limited. The aim of our study is to estimate the association of early-life exposure to ambient PM2.5 with child health outcomes (height-for-age) in India. METHODS: We linked nationally-representative anthropometric data from India's 2015-2016 Demographic and Health Survey (n = 218,152 children under five across 640 districts of India) with satellite-based PM2.5 exposure (concentration) data. We then applied fixed effects regression to assess the association between early-life ambient PM2.5 and subsequent height-for-age, analyzing whether deviations in air pollution from the seasonal average for a particular place are associated with deviations in child height from the average for that season in that place, controlling for trends over time, temperature, and birth, mother, and household characteristics. We also explored the timing of exposure and potential non-linearities in the concentration-response relationship. RESULTS: Children in the sample were exposed to an average of 55 µ g/m3 of PM2.5 in their birth month. After controlling for potential confounders, a 100 µg/m3 increase in PM2.5 in the month of birth was associated with a 0.05 [0.01-0.09] standard deviation reduction in child height. For an average 5 year old girl, this represents a height deficit of 0.24 [0.05-0.43] cm. We also found that exposure to PM2.5 in the last trimester in utero and in the first few months of life are significantly (p < 0.05) associated with child height deficits. We did not observe a decreasing marginal risk at high levels of exposure. CONCLUSIONS: India experiences some of the worst air pollution in the world. To our knowledge, this is the first study to estimate the association of early-life exposure to ambient PM2.5 on child height-for-age at the range of ambient pollution exposures observed in India. Because average exposure to ambient PM2.5 is high in India, where child height-for-age is a critical challenge in human development, our results highlight ambient air pollution as a public health policy priority.

Sanitation and Religion in South Asia: What Accounts for Differences across Countries?

Exposure to open defecation has serious consequences for child mortality, health, and human capital development. South Asia has the highest rates of open defecation worldwide, and although the incidence declines as household income rises, differences across South Asian countries are not explained by differences in per capita income. The rate of open defecation in sub-national regions of Bangladesh, India and Nepal is highly correlated with the fraction of the population that identifies as Hindu, in part because certain rituals of purity and pollution discourage having latrines in close proximity to one's home. Almost all open defecation occurs in rural areas, and this paper estimates how much the rate could be reduced if rural households in regions that have a higher fraction of Hindus, where open defecation is still common, altered their behaviour to reflect that of non-Hindu households in regions that are predominantly non-Hindu, where the rate of open defecation is much lower. Using nonparametric reweighting methods, this paper projects that rural open defecation in Bangladesh, India, and Nepal could be reduced to rates of between 6 and 8 per cent, compared to the prevailing level of 65 per cent.

Switching to sanitation: Understanding latrine adoption in a representative panel of rural Indian households.

Open defecation, which is still practiced by about a billion people worldwide, is one of the most compelling examples of how place influences health in developing countries. Efforts by governments and development organizations to address the world's remaining open defecation would be greatly supported by a better understanding of why some people adopt latrines and others do not. We analyze the 2005 and 2012 rounds of the India Human Development Survey (IHDS), a nationally representative panel of households in India, the country which is home to 60% of the people worldwide who defecate in the open. Among rural households that defecated in the open in 2005, we investigate what baseline properties and what changes over time are associated with switching to latrine use between 2005 and 2012. We find that households that are richer or better educated, that have certain demographic properties, or that improved their homes over this period were more likely to switch to using a latrine or toilet. However, each of these effect sizes is small; overall switching to latrine use from open defecation is low; and no ready household-level mechanisms are available for sanitation programs to widely influence these factors. Our research adds to a growing consensus in the literature that the social context should not be overlooked when trying to understand and bring about change in sanitation behavior.

Understanding Open Defecation in Rural India: Untouchability, Pollution, and Latrine Pits.

India has far higher open defecation rates than other developing regions where people are poorer, literacy rates are lower, and water is relatively more scarce. In practice, government programmes in rural India have paid little attention in understanding why so many rural Indians defecate in the open rather than use affordable pit latrines. Drawing on new data, a study points out that widespread open defecation in rural India is on account of beliefs, values, and norms about purity, pollution, caste, and untouchability that cause people to reject affordable latrines. Future rural sanitation programmes must address villagers' ideas about pollution, pit-emptying, and untouchability, and should do so in ways that accelerate progress towards social equality for Dalits rather than delay it.

An Experiment with Air Purifiers in Delhi during 2015-2016.

Particulate pollution has important consequences for human health, and is an issue of global concern. Outdoor air pollution has become a cause for alarm in India in particular because recent data suggest that ambient pollution levels in Indian cities are some of the highest in the world. We study the number of particles between 0.5µm and 2.5µm indoors while using affordable air purifiers in the highly polluted city of Delhi. Though substantial reductions in indoor number concentrations are observed during air purifier use, indoor air quality while using an air purifier is frequently worse than in cities with moderate pollution, and often worse than levels observed even in polluted cities. When outdoor pollution levels are higher, on average, indoor pollution levels while using an air purifier are also higher. Moreover, the ratio of indoor air quality during air purifier use to two comparison measures of air quality without an air purifier are also positively correlated with outdoor pollution levels, suggesting that as ambient air quality worsens there are diminishing returns to improvements in indoor air quality during air purifier use. The findings of this study indicate that although the most affordable air purifiers currently available are associated with significant improvements in the indoor environment, they are not a replacement for public action in regions like Delhi. Although private solutions may serve as a stopgap, reducing ambient air pollution must be a public health and policy priority in any region where air pollution is as high as Delhi's during the winter.

Disease externalities and net nutrition: Evidence from changes in sanitation and child height in Cambodia, 2005-2010.

Child height is an important indicator of human capital and human development, in large part because early life health and net nutrition shape both child height and adult economic productivity and health. Between 2005 and 2010, the average height of children under 5 in Cambodia significantly increased. What contributed to this improvement? Recent evidence suggests that exposure to poor sanitation - and specifically to widespread open defecation - can pose a critical threat to child growth. We closely analyze the sanitation height gradient in Cambodia in these two years. Decomposition analysis, in the spirit of Blinder-Oaxaca, suggests that the reduction in children's exposure to open defecation can statistically account for much or all of the increase in average child height between 2005 and 2010. In particular, we see evidence of externalities, indicating an important role for public policy: it is the sanitation behavior of a child's neighbors that matters more for child height rather than the household's sanitation behavior by itself. Moving from an area in which 100% of households defecate in the open to an area in which no households defecate in the open is associated with an average increase in height-for-age z-score of between 0.3 and 0.5. Our estimates are quantitatively robust and comparable with other estimates in the literature.