Sunday, July 2, 2017

The "Natural Rate" of Population Growth?

The population growth rate graph, again:

Graph #1: A Natural Rate of Population Growth?
I put a line on there in red, suggesting what looks to me to be a "natural" rate of population growth since the 1960s, or anyway a rate from which the actual rate is sometimes disturbed and to which it apparently desires to return.

Don't be outraged; it's just an impression.

Anyway, when I look at the blue line after 1960 I see what looks like one particularly large and long-lasting disturbance:

Graph #2: A Large Disturbance beginning around 1990
For some reason, I had in mind that this large disturbance was a result of immigration as opposed to the other thing. I don't know why I thought immigration, but I did. For the longest time.

Maybe I read it somewhere, and then forgot. Anyway, I finally tracked it down and yes, it looks like immigration caused that disturbance. The next graph is part of an image presented by weforum:

Graph #3: from World Economic Forum
There looks to be a pretty consistent uptrend since about 1950 on this graph. But just around 1990 there is one particularly large spike. It shows a tripling, from about 600 thousand to about 1800 thousand immigrants, and it attributes the spike to "IRCA legislation".

I looked it up. IRCA is the Immigration Reform and Control Act of 1986. So yeah, immigration in this case. But I still see it as a disturbance or deviation from the "natural" tendencies which arise as an outgrowth of economic conditions.

1 comment:

The Arthurian said...

Ivan Kitov says there is a correction to population every 10 years, as a result of the census. He observes that
"I had to redistribute all known bumps back into their past and obtained relatively smooth time series. This simple procedure did not work well in 1991".