% us_counties.dbf file contains 1990 census information on:
(see arc_histmapd4.m demo file)

% results.data contains:
% col 1 area name
% col 2 zip code
% col 3 LATITUDE
% col 4 LONGITUDE
% col 5 POP1990
% col 6 population living in same house 5 years ago
% col 7 POP65PLUS population 65 years old or more
% col 8 EMPLOYMENT
% col 9 HOUSEHLDS
% col 10 MEDINCOME
% col 11 PCINCOME
% col 12 POVERTY
% col 13 NOHOUSES
% col 14 MEDRENT
% col 15 WHITEPOP
% col 16 BLACKPOP
% col 17 NATIVPOP
