This is so well done, Carlyn. Fascinating, clear, and elegantly written. The one point I might like to add regards height of the people of the Netherlands. The first shorter group, born in 1930, lived through a worldwide depression and the horrors and scarcities of World War 2. So, certainly, the latter-borns had better nutrition, and therefore grew to the famously tall Dutch heights. I've also wondered if their high consumption of dairy products spurts their height, as they drink far more milk than neighboring and shorter Belgium. The Japanese are also growing taller and one reason may be that over the last few decades, dairy consumption has become more prevalent in that country. (I am not saying that dairy products are necessary or good for our health, just that they may be the source of increased height.)