History in Statistics

I was at a meeting in the Battambang Provincial Heath Office yesterday and the following graph was on the wall I was facing over the heads of the government counterparts with whom we were having a discussion.


This is a "population pyramid", a common way of presenting a country's population by age (you can double click on the graph to make it bigger). The Y axis is composed of 5 year age tranches, Zero through 4, 5 through 9, etc. The red are males, the green are females. The numbers at the end of each bar represent the percentage that tranche represents of the population. So female 5-9 year olds represent 7.9% of the total population.

The interesting thing here is that 20-24 age tranche which is significantly smaller than would be expected (normally these pyramids are completely smooth, the only part that changes is the "steepness" (everyday language for "slope" in statistics) of the sides, developed countries have steeper sides because the population lives longer and has fewer children.

The 20-24 year olds in this graph represent those kids that would have been born a year or so into the Khmer Rouge years until a year or so after the Vietnamese invaded and overthrew the Khmer Rouge. There were undoubtedly two aspects to this, fewer women were getting pregnant, and more infants were dying. The result, a lot fewer surviving children, and now a lot fewer adults in that age group (this data was collected in 2001 or 2002, so the age tranche today would be adults somewhere around the ages of 28-33.

War doesn't only affect the present, it affects the future as well.