Net Migration is a key component of population growth in Florida. It is defined as either in-migration or out-migration. In this Atlas, in-migrants are defined as anyone moving into a county; out-migrants are anyone moving out of a county. Most of Florida’s counties rely heavily on migration for population change.
Data on births and deaths are considered to be more reliable (and more likely to be available) than data on in-migration and out-migration; thus, one can only estimate the effects of the two migration processes on the growth of a population. In this Atlas, net migration is estimated using population estimates for two different years and births and deaths data for the period between those two years, as detailed in the following formula:
Population Change - Natural Increase = Net Migration
(2010 population – 1970 population) (Births – Deaths) (In-migrants – Out-migrants)
While this formula provides an estimate of net migration in Florida, it does mask trends in immigration and out-migration.
Between 1970 and 2006, migration in Florida accounted for over 80% of population growth. Starting in 2007, net migration for Florida as a whole fell sharply. Most counties in Florida have positive net migration, or more in-migrants than out-migrants. The formula for natural increase is:
Births - Deaths = Natural Increase
If this number is negative it indicates a decrease in natural increase, or fewer births than deaths. The number of births and deaths, along with fertility and mortality rates, vary from place to place. In some areas of Florida, deaths actually outnumber births, mainly due to the high numbers of elderly people settling, and subsequently dying, in those areas. The Bureau of Vital Statistics maintains reliable data on births and deaths in Florida.