Global average life expectancy was 24 years in 1000 AD, 31 years in 1900 and reached 66 years in 1999. It is widely assumed that, because at any one time 'wealthier is healthier', income growth must be the most important causal factor in worldwide health improvements. In fact, there is plentiful evidence suggesting otherwise. Income may have a role, but it is not the major factor behind improved levels of global health. For example, modern Vietnam has the same income per capita as the UK early in the Nineteenth Century. Yet life expectancy at birth in Vietnam today is 69 years as opposed to 41 years in the UK in the 1800s. And Infant mortality is less than one quarter of the level of the UK two hundred years ago. Furthermore, life expectancy has seen dramatic improvements even in countries that have seen zero or negative income growth over the past few deacades --Angola, Cuba and Nicaragua all followed this pattern, for example.
Instead, the history of health suggests that technological and institutional change has been key to advance. The British Industrial Revolution was associate with lower levels of health until massive public water and sanitation projects in the second half of the Nineteenth Century. Filtration and chlorination then played a large role. The spread of vaccination has proven vital in wiping out a number of major killers. Such interventions can be achieved at low (and dropping) levels of income, with the cost of a basic package of primary health care costing less than one percent of GDP even in the poorest countries. It is primarily institutional, rather than financial, barriers that stand in the way of improved health.
A similar conclusion applies to levels of violence --both warfare and individual acts of murder. Technology has been a factor beheind the growing power of the state to kill, but institutions rather than incomes appear to be more important in restraining acts of state violence. Institutional and social change also appears to have played the larger role in increasing the efficacy of state attempts to reduce unsanctioned violence.