a factor with levels alameda, ca
allegheny, pa
bergen, nj
bexar, tx
contra costa, ca
cook, il
cuyahoga, oh
dade, fl
dallas, tx
dupage, il
essex, ma
essex, nj
fairfax, va
fairfield, ct
franklin, oh
fresno, ca
fulton, ga
harris, tx
hartford, ct
hennepin, mn
honolulu, hi
jefferson, ky
king, wa
los angeles, ca
maricopa, az
marion, in
middlesex, ma
middlesex, nj
milwaukee, wi
new york, ny
norfolk, ma
oakland, mi
orange, ca
orange, fl
palm beach, fl
philadelphia, pa
pima, az
san bernadino, ca
san francisco, ca
santa clara, ca
st. louis, mo
suffolk, ma
ventura, ca
wayne, mi
worchester, ma