Portfolio.com rated the attractiveness of 157 markets for retirees based on six statistical indicators. Here are the details:

Goal: The study’s objective was to identify the nation’s most popular retirement areas. It gave the highest marks to communities where the population of seniors (65 or older) is already substantial and is growing rapidly.

Markets: The study covered the 157 metropolitan and micropolitan areas where at least 40,000 residents are classified as seniors. They ranged from the New York City area, with 2.48 million seniors, to Visalia, California, with 40,710.

Source: The study’s six statistical indicators were generated from raw data collected by the U.S. Census Bureau’s 2009 American Community Survey. Results of the ACS were released in September 2010.

Factors: Portfolio.com rated each area in the six categories below. The highest scores in each category went to the markets described in parentheses.

1. Seniors as share of total population—Percentage of all residents who are 65 or older. (Highest scores: largest percentages.)
2. Median age—The market’s midpoint age, with half of all residents being older and half being younger. (Highest scores: oldest medians.)
3. Seniors born out of state—Percentage of all seniors who were born in a different state from their current state of residence. (Highest scores: largest percentages.)
4. Incoming seniors—Percentage of all seniors who moved to their current county of residence from another county (or nation) during the previous 12 months. (Highest scores: largest percentages.)
5. Difference in out-of-state births—Comparison of the percentages of seniors and younger residents (64 or younger) who were born out of state. (Highest scores: largest advantages for seniors.)
6. Difference in incoming rates—Comparison of the percentages of seniors and younger residents who moved to their current county from another county (or nation) during the previous 12 months. (Highest scores: largest advantages for seniors.)

Availability: Some, but not all, of the statistics for each market are provided in chart form with this report.

Formula: Each area’s statistics were compared against the averages for the study group in all six categories. Above-average performances earned positive scores, while below-average results received negative scores. Each area’s six category scores were totaled to determine its overall rank, with the first four factors counting for 20 percent each and the final two factors for 10 percent each. Final scores ranged from 19.119 points for Bradenton-Sarasota, Florida, to negative-8.660 for Ogden, Utah.

Click here to see the best U.S. destinations for retirees.