One netter over xys excitedly claimed that he finally reached the half-winner level: his salary went up to six digit level. Well, if his wife is also working, his family income now ranks among top 2% in the US, although probably at the low bound. I heartily congratulate his success.

It is not a state secret that money can buy everything (including love ). However, here I voluntarily confine myself to the topic of money and health, leaving the chit-chat to other romantic observers.

Let’s review some economic facts to define who the poor and not-so-poor people are, thus boosting your self-esteem a little bit more.

According to the current population survey (CPS 2003), the median income in the US was about $43,000, and residents in the top rich states had the median income above $55,000. However, in 2003, the bottom 20% US population only accounted for 3.4% of aggregate income in the US, with an average income of $17,984, while the upper 20% household had average income of $86,867, which accounts for 50% of total US income (Census CPS income report 2004). The Gini index in 2003 is 0.464, higher than that in 1995 (the larger Gini index, the worse). Further, 12.5% people living under the official poverty rate (about $15,000 with a family of four), or about 35.9 million people are considerably poor.

It is kind of appalling when you realize that one out of ten people is living under poverty. Where are they? In all urban cities, many poor people live in the crowd central areas. They are working in labor intensive, low grade jobs such as cleaner, janitor and manufacturing positions. They are sort of invisible for many winners.

One doesn’t have to fumble through research papers to discover that poor people constantly suffer from chronic diseases and die earlier. The richer, on the other hand, enjoy much healthier and longer lives, in addition to all luxuries specifically made for them.

Apparently, the money in one’s pocket makes difference. Then, how?

Although the redistribution of income through tax and public subsidies such as Medicaid, SCHIP is important and complicate by itself, my primary interest in this essay is mechanisms of income to health.

The first intuitive explanation is that the absolute amount of money determines the life expectancy. People with more money can afford better living conditions, more healthy foods, and better health insurance. One may even further conclude that higher education incurs better job and higher income. People with higher education live in a healthier lifestyle. This argument seems justifiable and indeed correct.

However, in the relationship between income and health, the right tail is flat: the effects of income on health diminish as income goes up to a certain level. Further, at the low end, one may expect that income has larger effects on health, but it is not. The shape is sort of flat too (poor people can have free health insurance in most industrialized countries). Probably the most evident association is in the middle of curve, more money, better health.

Wilkinson in the UK made a sparkling discovery when he graphed life expectancy against Gini index by countries. The smaller Gini index, the longer life expectancy (except for the US). Although his findings were later discredited due to its outdated data, his hypothesis lingered. He proposed that income inequality could explain some of the health inequality, which has been verified by the British and Canada studies. It should be warned that the income inequality is an aggregate measure, i.e., a summary measurement at state level or country level, in contrast to individual income and education which are the characteristics of individuals. Some found no income inequality effects after adjusted for individual education and income using multilevel analysis (contextual analysis). Nevertheless, the inequality hypothesis gained strong support from US data.

It seems difficult to explain the mechanism from income inequality to health. Some believe that absolute amount of money is the key. However, in England and Canada where universal health insurance exists, the effect of regional income inequality on health persists. Some believed that income inequality itself may have direct effect on health.

Some propose that relative income level compared to the upper income level, or later relative deprivation compared to the lower income, or derivatives of the income curve, may independently explain the income inequality effects on health. As we all know, the feeling that one does not earn enough money certainly affects one’s psychological status. Those who have relatively lower income level are worse in health because anxiety, stress, and even failure are detrimental to health. This psycho-social theory has some supports but there are challenges. For example, the stress of daily life experienced by a poor people may be no worse than the stress from incoming review meetings experience by a manager. There is no way to tell that this stress is more harmful to health than the other one.

Some suggest that if one lives in relatively poor, he lacks social capital such as community support, trust, and networks. Then one may tease that the scope of social capital is so vast that it literally includes everything.

This relative thing can be extrapolated to a broader framework such that it embraces the relative social position, social class, and finally socio-economic position. Not only the money matters, but also the social status determines your fate. Among them, income, education, and employment are the most important things.

A recent terminology emerges in some popular media. Health literacy refers to the knowledge of health. Poor people may lack the health literacy while those rich people know more about health issues. Again, one may comment that health literacy is more related to education than income.

When it comes to sociology, complementary or competing theories are all around. One has to be critical to fully appreciate the “development” of our knowledge.