Fertility & Mortality

I had mistakenly put the 7 billion day in my Outlook calendar as October 18th 2012. The reality is that the United Nations announced that the world population hit 7 billion humans on October 31, 2011 - a year earlier!!   Naturally the statistician in me wondered why I was off by a year?  And how could the various news articles have such wide variation in forecasted dates?

Here is what the news articles have reported:

1804 - 1 Billion
1927  - 2 Billion  -  123 years
1959  - 3 Billion   -  32 years
1974  - 4 Billion    - 16 years
1987 -  5 Billion    -  13 years
October 12, 1999   6 Billion  -  12 years
October 31, 2011   7 Billion  -  12 years

2023, 2025   8 Billion -  12 to 14 years
2041 , 2050  9 Billion  -  16 to 27 years
2081, 2083  10 Billion  -  31 to 42 years

It all comes down to fertility rates and morality rates.  Even small variations in these rates of change create huge fluctuations in yearly forecasts and it appears the most sensitive variable is fertility!

With just a small change in fertility the estimate of world population by the end of the century (2100) varies between 6.2 billion to 15.8 billion.   YES even a possible prediction of population DECLINE!  That is with an assumption that life expectancy will increase from 68 years to 86 years by the turn of the century.

Why is this important?  Because living in a world with flat population or declining population will be VERY DIFFERENT from the world we have experienced so far. 

Mark your calendars now - October 15, 2024 - 8 Billion!


PS - Population this moment  - U.S. 314,500,734World 7,043,098,14214:55 UTC (EST+5) Oct 02, 2012