Sunday, January 25, 2009

Exponential Population Growth

Not everyone understands the idea of exponential growth. However, most people appreciate that this term means, in a generic sense, very rapid or ever increasing growth. The most common example of exponential growth is compound interest on an account in the savings bank which, if allowed to accumulate, causes the account balance to grow exponentially. One dollar at an interest rate of 5 % / year (0.014%/ day) compounded daily and continuously will grow in 500 years to 72 billion dollars and the interest at the end of the 500th year would be coming in at the magnificent rate of $114 / second (A = p (1+r)^t = $1 (1+.00014)^182500 = $72 billion). If left untouched for another doubling time of 14 years, the account balance would be 144 billion dollars and the interest would be accumulating at the rate of $228 / second. Of course, the purchasing power of the resulting amounts would be reduced by inflation and the net would be reduced by income taxes. Nevertheless, the effect of exponential growth is impressive.

The concept of exponential growth is also applicable to population growth. Since 1950, the world population growth rate has never been less than 1.6% per year and, in the recent past, has been as high as 2.1%. If the former growth rate continues, the 1995 world population of 5.7 billion will increase to 7.1 billion by the end of 2009 and 13.6 billion by 2050. In the U.S., application of the 1.6% rate of growth would mean our present population of about 303 million would grow to 581 million by 2050. That is substantially higher than the current Census Bureau forecast. Although over the long term, the U.S. growth rate is expected to exceed that of the world, the present U.S. rate at 0.883% is only about half that of the world population growth rate. Nevertheless, at the rate of 0.883% per year, there will be 434-439 million inhabitants in the U.S. by 2050 and 674 million by 2100. The Census Bureau estimate for 2100 is somewhat less than that but still between 500-600 million.

Professor Bartlett (see his bio below) asks succinctly: “Can you think of any problem in any area of human endeavor on any scale, from the microscopic to global, whose long-term solution is in any demonstrable way aided, assisted, or advanced by further increases in population, locally, nationally, or globally?” Why are our politicians being so obtuse about this?

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