what did New York do to lose five seats in 1980?

[jimrtex]

what's interesting is that even Nassau County lost population. Wasn't this an area of the postwar boom in home construction a la Levittown?

You end up with unusual age patterns.   From 1960-1970, Suffolk grew by 67%, while Nassau grew 10%.   Nassau was getting filled up.  Levittown was almost stagnant.

In 1970, Nassau males 45-54 outnumbered males 25-34 by 74%.  It was somewhat less pronounced among females 45-54 (48%).   Males 55-59 outnumbered females 55-59, by 3%; while in the 25-34 range, females outnumbered males by 21%.   So there is probably a combination of effects of different ages between grooms and brides; divorce; second marriages.

By 1980 the lack of persons of child-bearing age plus the baby bust are profound.  In Nassau, the ratio of graduating seniors to first graders is around 2 to 1.

Children 5-9 declined by over 40% between 1970 and 1980.  The fastest growing population was actually 25-34, as the children of the post-war boom come of age; plus you may have a new generation moving out from Queens and Brooklyn as the first owners of the homes are reaching retirement and downsizing or moving to Florida.   But these new homeowners aren't having children at anywhere near the rate of the earlier generation.

There are big drops in the 35-54 age brackets (20%) as the first generation ages, while those 55-64 increase by around 20%.

0-4  29%,30% decline
5-9  41%,43% decline
10-14 32%,33% decline
15-24 5% increase, 3% decline.
25-34 44%, 27% increase.
35-44 20%, 21% decrease.
45-54 22%, 13% decrease.
55-64 30%, 33% increase
65-74 32%, 16% increase

By 1990, you finish up the big drop in children and you're seeing the child-bearing adult group filling up, but not having as many children.

[jimrtex]

Rent control? Baby boom kids left the nest?

You take farm land and build a bunch of houses, and you are going to get a bunch of people in their 20's and early 30's.   If they have children, it is a toddler.   While an apartment is OK for a baby or toddler, not so much for older children, and you are concerned about the schools.

10 years later, and you have parents in their 30s, and a bunch of grade-school age children.  Few of the houses are sold.   There are some divorces, and perhaps the largest families with 6 or more children buy a bigger house, but there isn't much opportunity for newly formed families.

20 years later, and you have parents in their 40s, and early 50s and they've finished up having children and the oldest children are going off to college.  There isn't a market for apartments.

30 years later and the grade schools are depopulating.  Some of the houses are becoming available, as the original owners are retiring and moving to Florida, or moving to condos or townhouses, which may be built as developers start finding smaller areas to build on.

Between 1970 and 1980, Nassau saw massive drops in young children; some drop in late teenagers as the youngest children of the earliest settlers reached high school.  There was actually a pretty big increase in persons in their 20s, as all the original owners had aged way past that (in 1970 the largest age cohort was 45-54).  So in the 70s, at least some of the children of the settlers were sticking around - but not having as many children, and also having them later.

But there were big drops in the 35-54 population, as the settlers aged, and increases in the older population.

Most of the population drop was due to children not being replaced, while the distribution of the adult population was changing.

[jimrtex]

Most of the population drop was due to children not being replaced, while the distribution of the adult population was changing.

Total population is the number of housing units multiplied by the average number of person per household [plus homeless people.] Nassau suffered the combined effects of the ending of the build out, and the drop of birthrates. But, New York state as a whole suffered a decline in population more than the nation's. Presumably, the New Yorkers in their 20's could have lived in another county, or new housing could have been constructed farther out from Manhattan.

Most of the decline in Nassau County in 1980 was among children.  It was precipitous, with a 40% decline in 5-9 YO.

The population between 20-34 was increasing (44% among 25-34 males; 27% among 25-34 females).  This would be children from the early settlers sticking around, or a new group moving out from Queens and Brooklyn.  But housing would be limited.   It takes a while for apartments and condos to be built in an area where everyone's dream was to escape the tenements.  But the base population in 1970 in these age groups was low, since the original settlers were now in middle age.

So while between 1970 and 1980 the male 25-34 population increased by 44%; the male 35-44 population decreased by 20%.

The drop in the Nassau County population (10%) was due to the lack of new housing, and the rapid development 30 years earlier, with a side effect of the end of the baby boom.