Interesting census figures detailing the year round population on the island:

                        Avalon            Stone Harbor

1930                343                  363

1940                313                  383

1950                428                  670

1960                695                  834

1970                1,283               1,089

1980                2,162               1,187

1990                1,809               1,025

2000                2,143               1,128

2010                1,334               866

Observations: 

The decline in year round residents between 1980 and 1990; and again 2000 to 2010 is tied to the real estate boom in the middle of both decades.  Year round residents were able to “cash out” and purchase homes off of the island for much less. 

And, interesting to note that the population in Stone Harbor was greater than Avalon until the 1970s.  One reason could be that there were still large tracts of open land in Avalon.  The bay front lagoon area (Pelican Drive, etc.) and the streets behind the high dunes weren’t developed until the 1960s and 70s.

Data from the U.S Census Bureau report published in The Press of Atlantic City 4/15/12