50 Years of Population Growth in Isla Mujeres By Ronda Winn-Roberts

 These are calculated from the statistics given at the end, which are from the Urban Development document published on the municipal website. I rounded them and did the math & comparisons (and left out the stats for the whole municipality).

They are just for the island. (They do not include the Continental Zone of Isla Mujeres)

Each decade the island population grew approximately:
1960-1970 +1600
1970-1980 + 500
1980-1990 +7300
1990-2000 + 200
2000-2010 +2000

If you look at this in 20 year cycles:
1960-1980: +2100
1980-2000: +7500
or
1970-1990: +7800
1990-2010: +2200

Recent Growth Patterns:
1990-2000 +200
2000-2010 +2000 ~Past ten years
1990-2010 +2200 ~Past twenty years
vs.
1980-1990 +7300 Largest increase in a ten year period occurred ~twenty to thirty years ago.

Here's the island population:

1960  1071
1970  2663
1980  3164
1990 10,448 
1995   8482
2000 10,666
2005 11,325
2007 11,657
2010 12,642 
It is estimated that there are about 20,000 residents on the island now.