Friday, 4 March 2011

Population Pyramids in Action

Found a neat site where you can run an interactive population pyramid of several of the developed nations, including the US. 
As a cursor below the graph runs through the years, the pyramid shows the population distribution of males and females by age group.  You can stop it and a mouse-over will highlight the age group of each bar for males and females. 

Here is the present Graph showing that edge of the baby-boomers hitting the social security bracket, and two mild periods of reduced birth rates around 1990 and 1970 (why???... are these just the dampened oscillations of the baby-boom... born around 1950 we would have our children born around 1975-1980 and grandchildren around 2000 to 2005? or do they cue off economic boom and bust... what was the impact of Aids )

This one is for 1950, I had just moved into the second bar, and the peak of the baby boom was about to hit. In the next five years the population would grow from 159 million to 171 million. 
A little research suggested that the first population pyramid split by gender was created for the US census by General Francis Walker, who used them in the 1840, 1850, 1860 and 1870 census.  The image below is one such for the state of Nebraska which it seems is from the 1874 census data-book.  It was around this time that Heinrich Schwabe (who discovered that sunspots moved in ten-eleven year cycles) adjusted them to be more like bar graphs and they have changed little since that time. 

I also came across this interesting population "pyramid" which is in three dimensions.  It was by Luigi Perozzo and was modeled on the Swedish Census from 1750 to 1875.   The graph shows the number of births each year over the period, and then shows the population distributed by age in perspective for the census results each five year period.  The chart was presented, and apparenty well praised at the 1875 Geographic Congress and again at the 1878 Paris Exhibition. 


Steven Colyer said...

Correct me if I'm wrong, but the top year for American births was 1957. And I don't mean as a percentage of population, I'm talking about total number of births, and I believe that is still the record. Next up is 1989, and the next 4 of 5 would be around '57.

I seem to remember lots of talk about ZPG (Zero population growth) in the late 1960's. The invention of The Pill circa '63 may have had something to do with that.

In any event, interesting, thanks. I spent some time on Demographics yesterday, myself. Doing my usual thing, looking for a job, I was noting how devalued all homes in the US are. For some reason I visited the situation in "Titletown", Green Bay, WI, which led me to the "Yoopers" (U.P.ers), being the residents of Upper Peninsula, Michigan, where, alas, the population is in decline. They're almost all of Finnish heritage. Back to GB, Lambeau Field, if you Google Earth it, is right across the street from Suburbia.

Pat's Blog said...

Steven, as usual, your numbers are on the mark..or very nearly so... My data (source at bottom) shows that 2005 (the most recent year in this data) was above any year except 1990 of recent (post sixties)time.

1954 4,078,000 25.3
1955 4,104,000 25.0
1956 4,218,000 25.2
1957 4,308,000 25.3
1958 4,255,000 24.5
1959 4,295,000 24.3
1960 4,257,850 23.7
1961 4,268,326 23.3
1962 4,167,362 22.4

and then
1988 3,913,000 15.9
1989 4,021,000 16.2
1990 4,179,000 16.7
1991 4,111,000 16.2
1992 4,084,000 16.0
1993 4,039,000 15.7
1994 3,979,000 15.3
1995 3,892,000 14.8
1996 3,899,000 14.7
1997 3,882,000 14.5
1998 3,941,553 14.6
1999 3,959,417 14.5
2000 4,058,814 14.7
2001 4,025,933 14.1
2002 4,021,726 13.9
2003 4,089,950 14.1
2004 4,112,052 14.0
2005 4,138,349 14.0

The CDC gives "Data for United States in 2009
Number of births: 4,131,019 "

but also that "Fertility rate: 66.7 births per 1000 women aged 15-44 years ---Percent unmarried: 41.0%

Live Births and Birth Rates, by Year —

Pat's Blog said...

Oops, one more from the CDC..
"This continues a decline in the number of births from an all-time high of 4,316,233 in 2007 (2)."

Steven Colyer said...

"very nearly so" is right on the money, Pat. That data re 1957 and 1989 (the year of my first kid's birth) are probably from the early 90's so I'm not surprised it's changed but ... what doesn't?

Wow, "the early 90's". That seems like yesterday to you and me, but when you think about it ... that's when your students were born!

Ai chi wawa, where'd the time go? ;-)