The [[positive correlation between health and income per capita is one of the best-known relations in international development]] (see figure). This correlation is commonly thought to reflect a causal link running from income to health. Higher income gives greater command over many of the goods and services that promote health, such as better nutrition and access to safe water, sanitation, and good quality health services. Recently, however, [[another intriguing possibility has emerged: that the health-income correlation is partly explained by a causal link running the other way—from health to income]]. How this could be? ## 1. Productivity Healthier people, higher labor productivity. Fewer lost workdays from illness or the need to care for other family members who have fallen ill. ## 2. Education Healthier people who liver longer have stronger incentives to invest in developing their skills, because they expect to reap the benefits of such investments over longer periods. Good health also promotes school attendance and enhances cognitive function. ## 3. Investment in physical capital Improvements in longevity create a greater need for people to save for their retirement. Insofar as increased savings lead to increased investment, workers will have access to more capital and their incomes will rise. In addition, a healthy and educated workforce acts as a strong magnet for foreign investment. ## 4. Demographic dividend The transition from high to low rates of mortality and fertility has been dramatic and rapid in many developing countries in recent decades. Mortality declines concentrated among infants and children typically initiate the transition and trigger subsequent declines in fertility. An initial surge in the numbers of young dependents gradually gives way to an increase in the proportion of the population that is of working age ([1](https://www-science-org.ez.lshtm.ac.uk/doi/10.1126/science.287.5456.1207#core-R1)). As this happens, income per capita can rise dramatically, provided the broader policy environment permits the new workers to be absorbed into productive employment ([2](https://www-science-org.ez.lshtm.ac.uk/doi/10.1126/science.287.5456.1207#core-R2)). [[Health improvements fortify the economy and alleviate poverty]] [[Direct effects of life expectancy on economic growth are important and indirect effects of improvements in health status that operate via demographic change also is]] Example of East Asia between 1965-1990 that the working-age population grew several times higher than the dependent population. The process have been triggered by declining child and infant mortality, itself prompted by the development of antibiotics and antimicrobials (which were discovered and introduced in the 1920s, 1930s, and 1940s), the use of DDT, and the classic public health improvements related to safe water and sanitation. In conclusion, health improvements is one of the major pillars upon economic development were based. In contrast, poor health can slow the demographic transition and inhibit growth. Diseases burden induces many families to dissipate their resources among large numbers of children, creating a high-fertility, high-mortality poverty trap that impedes economic growth. Energy use: rural poor rely heavily on wood, dung, and other biomass, that in turns generate indoor air pollution. Infant and child mortality rates are elevated, and life expectancy is diminished. Fertility rates are also high, partly to ensure enough children for firewood collection. Slow income growht is the end result. ## Mutual reinforcement [[Interesting Phrase]] Economists initially believed that income will improve health, but now we understand that there is mutual reinforcement (health also stimulate economic development) -> **virtuous spiral**. This “virtuous spiral” can transform an impoverished, disease-prone country into one that offers its people a much higher quality of life. Health improvements and economic growth can be mutually reinforcing in another way. As rising incomes cause fertility to decline, there are consequent benefits to the health of mothers and children, via longer breast-feeding, less stress on women's reproductive systems, more opportunities for them to work outside the home, and increased resources for each child's upbringing. In turn, declines in fertility promote economic growth by allowing more of society's resources to be devoted to urgently needed investments in physical capital, infrastructure, and educational quality. Regrettably, [[the mutual reinforcement between health and income can also operate in reverse. Declines in health status in some parts of the world are having staggering impacts on economic well-being]]. The AIDS epidemic in Africa is perhaps the most prominent example. About 8% of African adults are now HIV positive, with 56% of Sub-Saharan Africans not expected to reach age 60 ([11](https://www-science-org.ez.lshtm.ac.uk/doi/10.1126/science.287.5456.1207#core-R11)). ## Health-Led Development [[Health-led development means investing in health is not the means of its end but rather as a direction to stimulate development]] >Conventional wisdom holds that income growth results in improved health, but that is only part of the health-income story. The remainder concerns the role of health as an instrument of self-sustaining economic growth and human progress. Poor [[health is]] more than just a consequence of low income; it is also one of its fundamental causes. To be sure, health and demography are not the only influences on economic growth, but they certainly appear to be among the most potent. A revolution in economic thinking has taken place over the past few decades, putting human capital, particularly educated workers, on a par with physical capital as an input into production. We would argue that increased [[health is]] another aspect of human capital that also enters into production. In addition, long life expectancy may be the fundamental force that creates the demand for education and encourages the domestic saving that is a key determinant of economic growth. This perspective offers an exciting new possibility in international development: investing in health to help stimulate development. A focus on health cannot be the sole approach to improving living standards, nor may it even be the best. However, the evidence for viewing health as one of the more effective arrows in the development quiver is surely growing stronger.