Mao Wuz Here: The Great Leap, Uh, Forward?

Originally posted at Science 2.0 on 16 December 2009.

I came across this graph from the US Census Bureau on io9. They project the linear trend after 1965 out to 2050, assuming no major changes, which is always dangerous. The short story is that the Ehrlichian fear of massive overpopulation may not come true due to worldwide reductions in population growth. The human population might peak in the not so distant future. I might have to rethink my prediction of when evolution will finally vanquish creationism/intelligent design.

But, let’s ask the real question. What the hell happened in 1960?

Inspired by Steven Levitt to flip the bird to subject matter expertise, I went and grabbed me some Wikipedia statistics; specifically, world population statistics in five year increments since 1950. From these, I calculated** growth rates over those five year increments with no future projection. Although the scale is different due to my rates being 5-year rates, this matches the trends seen in the Census Bureau’s yearly growth rate data including what I shall call the 1960 Valley, for lack of a better term.

The Wikipedia data had geographic breakdowns of the data, which I used to find growth rates for each region. I also calculated an “expected growth rate” for 1960 based on making 1955-1960-1965 a linear trend without the valley. It was as if the 1960 Valley never happened. From the “expected growth rate”, I could calculate the number of people that must be “missing” to cause the 1960 deviation, if any existed in the population. Because birth rates are generally controlled by long term societal trends, but death rates can be suddenly increased by singular historical events, I am interpreting “missing” as “died”.

When broken down by region, only Asia (red) and Latin America (dark blue) experienced the 1960 Valley***.  The 1960 Valley equates to ~31 million missing worldwide with ~22 million missing from Asia and ~4.5 million people missing from Latin America.

There are only a few types of events that could cause ~22 million excess deaths in five years: war, disease, famine, and large meteor impact. Could I find such an event for Asia around 1960? Indeed, I could. Famine and natural disasters during China’s “Great Leap Forward” program is estimated to have killed 20-30 million people between 1959-1961, in total agreement with the prediction. I have not yet been able to find an event or a series of events that can account for the ~4.5 million missing in Latin America.

Because Asia has roughly half of the world’s population, any fluctuation in the Asian population will also dramatically affect worldwide statistics. The “Great Leap Forward” famine was responsible for the 1960 Valley.

Adapted from original by the rugbyologist

So, what happened in Latin America around 1960 to cause ~4.5 million people to go missing? It seems to me that if ~4.5 million people go missing over five years, we should be aware of it. Any ideas?

*Although I’m certain that this solution to the 1960 Valley is obvious and well-known to anyone with a smidgen of background in population demographics, I find situations like this to be a great opportunity to no only apply critical thinking skills to an apparent anomaly, but to also use some critical analysis to make a prediction and check that the prediction is correct.
**All “calculations” should be taken as back of the envelope. No fancy population growth models for me. At least not during the holiday season.
***Europe appears to have a very tiny valley in 1960 (~1 million missing) when compared to 1965. Europe, however, is generally in a growth rate decline over the entire data set and 1960 seems to be more linear with 1970-2005, suggesting that 1965 is an aberrant uptick in growth.

Author: Josh Witten

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