POPULATION CONTROL REVISITED

It is now almost six years since I dealt with questions of fer-tility and population control [AtE Feb 86], and it is time to revisit it, for it appears that the fertility rate, after its fastest and lowest drop in US history, is now either stabilizing or turning round.

The fertility rate is the average number of births per woman in her fertile years (age 15-44, by the US Bureau of the Census definition), and the reason why this parameter is so crucial is that it forecasts population growth rather than looking at the present size or the population.

Several readers have written to me saying "I agree with what you say about radiation, global warming, ozone layer, and every-thing else except the issue of population growth. How can you make light of it when the US population keeps increasing all the time?"

Of course it is increasing. The Baby Boomers of 1957 (fer-tility rate 3.767) are now 35 years old; they have children who in another 5 years will begin to have more children, keeping the population growing. But the generation of the fertility rate mini-mum (1976, fertility rate 1.738) are now only 16 and most will not have children for some time.

The analogy I like to give is the rising and falling level of a river. If you look at it now, it does not tell you much about the spring floods. To forecast those, you don't look at the river, you look at the snow pack in the mountains. That is why I look at the fertility rate and not the population. It is the snow pack that tells you the future water level. It is not quite exact, because apart from the melting snow, the water level also depends on rain; neither is the fertility rate exact, because the population also depends on the death rate (when people live longer, the population increases). But even so, it tells you much more than just looking at the population directly.

Another way to look at this is the delay between cause and effect. When you strike the key of a piano, the sound is evoked al-most immediately. When you strike the key of a pipe organ, it takes a short, but perceptible time for the sound to begin after you have struck the key, which takes some getting used to for a pianist. If you strike the key of a word processor and send the instructions of the tune to be played to a pianist by the US Snail, it will take at least two days for the sound to begin, and if you have the slightest error in the address, the delay can take up to 6 months for a first class letter to be returned and the instructions to be mailed again.

Now how long does it take for the fertility rate (cause) to affect the population (effect)? Roughly the expectation of life at birth. And that, in 1989 (the last year given in the current Statistical Abstract) was 75.2 years! So don't wait for the sound, look at the finger striking the key.

If all women bore children, zero population growth (ZPG) would clearly be achieved for a fertility rate of 2.0, since on the average, male-female couples would only just reproduce them-selves. In fact, however, many women remain childless, especially due to the mortality of female infants, so the true number must be greater than 2.0. The number adopted for ZPG by the demo-graphers to account for this is 2.15.

[indicates a peak in fertility rate in 1957 (Baby Boom peak); 1968-Ehrlich publishes "Population Bomb" as fertility rate steeply declines from 1957 peak; 1972-ZPG point crossed; 1990-Ehrlich publishes "Population Explosion" -what a dirt bag; 1990-small increase in fertility rate noticed, still below ZPG.]

The ZPG level was crossed in the US in early 1972 (total for the year, 2.010), a mere four years after Ehrlich scared the world silly with his infantile Population Bomb, itself published 11 years after the maximum of 1957, during the steepest drop in fertility rate in US history.

The peak of 1957 was not the highest peak in US history (e.g., the peak of 1910 was higher), but the minimum of 1976 was the lowest ever. When it slowed down and even increased slightly, there was much debate whether this was a temporary aberration or a genuine turn-around. That debate is now over, as you can see from the figure, for it is no aberration: whether it is a genuine turn-around or possibly the beginning of a stabilization remains to be seen.