2005 Behavioral Risk Factor Surveillance System (BRFSS) Metropolitan Area Data Weighting Methodology

Creation of Metropolitan-Level Weights

A documented and verified subset of the 2005 BRFSS has been produced to provide some local area estimates.  These local areas are identified as metropolitan statistical areas (MSAs), primary metropolitan statistical areas (PMSAs), or New England county metropolitan statistical areas (NECMAs), as defined by the U.S. Office of Management and Budget and used by the U.S. Census Bureau in 1999.  In this report, all mentions of metropolitan area refer to MSAs, PMSAs, and NECMAs.  Detail information on MSA, PMSA, and NECMA designations used by the U.S. Census Bureau used in this analysis is available at 
http://www.census.gov/population/www/estimates/pastmetro.html.  The metropolitan area definitions used for this analysis were June 30, 1999, which are different from the definitions currently used in SMART data. The reason for using old definitions is to match the EPA data for it used the old definitions in their datasets.

The BRFSS 2005 metropolitan area data set was produced by adding new analysis weights designed to correspond to the 2005 population estimates for each eligible metropolitan area.  The additional weights were post-stratified to the metropolitan area level. The process by which these new weights were obtained is detailed in Appendix C, “Weight Class Collapsing Rules.”

Selected Areas 

Typically, BRFSS data are used to produce state-level estimates.  However, for this project, 2005 BRFSS data were used to produce prevalence estimates for metropolitan areas. Estimates have been produced for 86 metropolitan areas that have met the analysis criteria for the 2005 data year.   Missing county codes were imputed from a value included in the purchased telephone sample that represents the county most likely to be associated with the telephone number.  

Appendix A: Variables Added to 2005 Data

_PMSA—Metropolitan area code of the MSA, PMSA, or NECMA, if appropriate, in which the respondent lived.  

_PMSANAM—Metropolitan area name of the MSA, PMSA, or NECMA, if appropriate, in which the respondent lived.  

_PMSAWT—The new metropolitan area-level weight, which should be used when generating metropolitan area-level estimates for questions that were asked of the entire sample.  

Appendix B: The 86 Areas with Metropolitan Area-Level Weights in the 2005 BRFSS, with MSA, PMSA, or NECMA Codes and Names

MSA CODE	MSA NAME	
0200	Albuquerque, NM MSA	
0520	Atlanta, GA MSA	
0600	Augusta-Aiken, GA-SC MSA	
0640	Austin-San Marcos, TX MSA	
0720	Baltimore, MD PMSA	
0875	Bergen-Passaic, NJ PMSA	
1000	Birmingham, AL MSA	
1010	Bismarck, ND MSA	
1080	Boise City, ID MSA	
1350	Casper, WY MSA	
1440	Charleston-North Charleston, SC MSA	
1480	Charleston, WV MSA	
1520	Charlotte-Gastonia-Rock Hill, NC-SC MSA	
1580	Cheyenne, WY MSA	
1600	Chicago, IL PMSA	
1640	Cincinnati, OH-KY-IN PMSA	
1680	Cleveland-Lorain-Elyria, OH PMSA	
1760	Columbia, SC MSA	
1840	Columbus, OH MSA	
1920	Dallas, TX PMSA	
2080	Denver, CO PMSA	
2120	Des Moines, IA MSA	
2160	Detroit, MI PMSA	
2190	Dover, DE MSA	
2520	Fargo-Moorhead, ND-MN MSA	
2680	Fort Lauderdale, FL PMSA	
2800	Fort Worth-Arlington, TX PMSA	
3000	Grand Rapids-Muskegon-Holland, MI MSA	
3120	Greensboro--Winston-Salem--High Point, NC MSA	
3160	Greenville-Spartanburg-Anderson, SC MSA	
3320	Honolulu, HI MSA	
3360	Houston, TX PMSA	
3400	Huntington-Ashland, WV-KY-OH MSA	
3480	Indianapolis, IN MSA	
3560	Jackson, MS MSA	
3640	Jersey City, NJ PMSA	
3760	Kansas City, MO-KS MSA	
4100	Las Cruces, NM MSA	
4120	Las Vegas, NV-AZ MSA	
4360	Lincoln, NE MSA	
4400	Little Rock-North Little Rock, AR MSA	
4480	Los Angeles-Long Beach, CA PMSA	
4520	Louisville, KY-IN MSA	
4920	Memphis, TN-AR-MS MSA	
5000	Miami, FL PMSA	
5015	Middlesex-Somerset-Hunterdon, NJ PMSA	
5080	Milwaukee-Waukesha, WI PMSA	
5120	Minneapolis-St Paul, MN-WI MSA	
5190	Monmouth-Ocean, NJ PMSA	
5360	Nashville, TN MSA	
5380	Nassau-Suffolk, NY PMSA	
5560	New Orleans, LA MSA	
5600	New York, NY PMSA	
5640	Newark, NJ PMSA	
5720	Norfolk-Virginia Beach-Newport News, VA-NC MSA	
5880	Oklahoma City, OK MSA	
5920	Omaha, NE-IA MSA	
5945	Orange County, CA PMSA	
5960	Orlando, FL MSA	
6160	Philadelphia, PA-NJ PMSA	
6200	Phoenix-Mesa, AZ MSA	
6280	Pittsburgh, PA MSA	
6440	Portland-Vancouver, OR-WA PMSA	
6520	Provo-Orem, UT MSA	
6640	Raleigh-Durham-Chapel Hill, NC MSA	
6660	Rapid City, SD MSA	
6720	Reno, NV MSA	
6760	Richmond-Petersburg, VA MSA	
6780	Riverside-San Bernardino, CA PMSA	
7040	St Louis, MO-IL MSA	
7160	Salt Lake City-Ogden, UT MSA	
7240	San Antonio, TX MSA	
7320	San Diego, CA MSA	
7490	Santa Fe, NM MSA	
7600	Seattle-Bellevue-Everett, WA PMSA	
7760	Sioux Falls, SD MSA	
7840	Spokane, WA MSA	
8200	Tacoma, WA PMSA	
8280	Tampa-St Petersburg-Clearwater, FL MSA	
8440	Topeka, KS MSA	
8520	Tucson, AZ MSA	
8560	Tulsa, OK MSA	
8840	Washington, DC-MD-VA-WV PMSA	
9040	Wichita, KS MSA	
9160	Wilmington-Newark, DE-MD PMSA	
9200	Wilmington, NC MSA	

Appendix C:  Weight Class Collapsing Rules

Metropolitan Area-Level Weighting Methodology

Respondents were assigned to a metropolitan area on the basis of the county name that they provided during the interview.  The county was then recorded using the Federal Information Processing Standards (FIPS) county code used by the U.S. Census Bureau.  

All respondents in metropolitan areas were then assigned to age, race, and sex categories.  If a respondent’s age was missing, it was imputed using the variable _IMPAGE available in the BRFSS public-use 2005 data file.  If a respondent’s race was missing, it was imputed using the majority race for the metropolitan area in which the respondent lived.  

Within each metropolitan area, respondents were assigned to weighting classes on the basis of age (18-24, 25-34, 35-44, 45-54, 55-64, or 65+), race (white and non-Hispanic, or nonwhite or Hispanic), and sex (male or female) categories.  Some states did not use race in post-stratification; for the metropolitan areas in these states, only age and sex groups were used to establish weighting classes.  For all other metropolitan areas, all three groups were used to establish weighting classes.  For metropolitan areas that crossed state lines, the post-stratification variables used by the state in which the majority of the metropolitan area’s population lived were used to set up weighting classes.  Thus, metropolitan areas that post-stratified by race had 24 initial weighting classes and metropolitan areas that did not post-stratify by race had 12 initial weighting classes.  

Weighting classes with fewer than 19 sample members were collapsed according to the following rules:

1.	For metropolitan areas that used race in post-stratification, the race categories within a sex category were collapsed if at least 80% of the age categories (i.e., at least five age categories) in the race and sex cross-classification had fewer than 19 members. 

2.	The two youngest age categories in any age-sex or age-sex-race weighting class were collapsed if either contained fewer than 19 members. The two middle and two oldest age categories in each remaining weighting class were also collapsed if either had fewer than 19 members. 

3.	Weighting classes were not collapsed across sex. However, for each age and race category collapsing, it was done in the same manner for the male and female.

4.	Metropolitan area was not included in the re-weighting if weighting classes with fewer than 19 sample members remained after all collapsing rules had been applied. 

In 82 metropolitan areas, at least 500 respondents participated in the 2005 BRFSS and at least 19 sample members remained in all final weighting classes.  A list of these metropolitan areas is available in Appendix B.  The respondents in these metropolitan areas were the only ones assigned a metropolitan area-level weight.  To calculate the new metropolitan area-level weight, we applied a post-stratification adjustment factor to the design weight (_WT2) and created the adjustment factor based on the ratio of the total population to the sum of the design weights for each weighting class within each metropolitan area.  The new metropolitan area-level weight (_PMSAWT) should be used to generate estimates in these 85 metropolitan areas.

Example—SUDAAN Code

For example, suppose we want a prevalence estimate for the Atlanta, GA metropolitan area  (PMSA code = 0520).  The SAS/SUDAAN code that could be used to generate this estimate is:

proc sort data=xxxx;
by _STSTR _PSU;
run;

proc descript data=xxxx filetype=sas design=wr;
nest _STSTR _PSU / missunit;
weight _PMSAWT;
subpopn _PMSA=0520 / name=” Atlanta, GA”;
var (your analysis variable);
catlevel (the level of your analysis variable for which you want an estimate);
run;