HEADWATERS ECONOMICS GEOGRAPHIC DATA LIBRARY DOCUMENTATION

TITLE: 	
Dataset Name: 		US Housing Affordablity (2000)
Dataset Type: 		ACCESS

GENERAL DESCRIPTION: 
This dataset calculates an approximate housing affordability index 
based on US Census data for median house prices and family income.  
The index is the ratio of the average family income divided by the 
income that would be required to qualify for the median house.
100 means that the average family could afford the median house in 2000.
Over 100 means the average family has more than enough income to qualify for the 
median house.

DATA SOURCE(S):  		US Census
Date of Original Source Data:	House Prices from 2000 (Income from 1999)

DATASET EXTENT:  		United States (US, States, Counties, County Subdivisions, Places etc...)
 
TABLES CODES AND VALUES: 

ITEM		ITEM DESCRIPTION
fips		5 digit county fips 
sumlev	Kind of Geography (County, State, Place, County Subdivision etc...)
GeoComp	Usually "00" for total
		Additional fields are required to specify different geographies.
		see USGEO in Access database for additional coding information.  USGEO contains
		the variables necessary to filter the records and is then joined to the data tables 
		by LOGRECNO.  Note that there are different LOGRECNO values for the same geographies in 
		the different Summary Files (SF1 vs. SF3).

Summary Files	SF1 (Short Form 100% Data) and SF3 (Long Form Survey Data)		

DATA LINEAGE SUMMARY: 
		The dataset was downloaded from the Census FTP site.  
		Housing Affordability Index was calulated by 
		Headwaters Economics but all of the component data are also available from
		American Factfinder except the interest rates.
		Formula uses 8.03% in 2000 and 10.01% in 1990 which are from the
		MBA Weekly Survey of Mortgage Applications Monthly Average Interest Rates On 
		30-Year Fixed-Rate Mortgages

Key:
IR = Interest Rate
MEDPRICE = Median price of existing single-family home sale
PMT= Monthly payment
MEDINC = Median Family Income
MINC = Necessary Monthly Income
QINC = Qualifying Income

Formula (based on formula used by the National Association of Realtors (NAR))
See http://www.realtor.org/:

Principle & Interest Payment – Monthly Payment
Formula: MEDPRICE*.8*(IR/12)*((1+(IR/12))**360/(((1+(IR/12))**360)-1)

Median as % of Income = Necessary monthly income
Formula: ((PMT*12)/MEDINC)*100

Qualifying Income – Income necessary to qualify for a loan for the median priced home
Formula: PMT * 4 * 12

Housing Affordability Index(Composite)- Measures the degree to which a typical family can
afford the monthly mortgage payments on a typical home.
Formula: (MEDINC/QINC)*100

DATA SOURCES CONTACT(S): 
Name: 		Phone Directory at http://www.census.gov/contacts/www/c-census2000.html
Abbr. Name:		US Census
Address:		U.S. Census Bureau
			4700 Silver Hill Road
			Washington DC 20233		
Phone:   		Phone Directory at http://www.census.gov/contacts/www/c-census2000.html
Email:   		pio@census.gov
Web site: 	  	http://www.census.gov/main/www/cen2000.html
          
HEADWATERS ECONOMICS CONTACT: 
Name:			Headwaters Economics Geographic Data Library
Abbr. Name:		HEGDL
Address:		Headwaters Economics
                  P.O. Box 7059, 
			Bozeman MT 59771 
                        
Web site:		http://www.headwaterseconomics.org
Contact Person:  	Jeff van den Noort
Phone:   		(406)599-1653
Email:   		jeff at headwaterseconomics.org