Accuracy of commercial geocoding: assessment and implications

Table 4 Overall match rate, census tract concordance and ρ ^a, by address and match characteristics

Characteristic	Stratum	Match Rate	Census Tract Concordance	ρ ^a
Address Source	EPA	62%	47%	1,619 (7,904)
	NGS	88%	72%	1,125 (3,711)
	WHI	98%	97%	159 (409)
Address Type	No Street Number	28%	8%	5,111 (6,150)
	Intersection	60%	43%	1,259 (6,270)
	Complete	82%	73%	793 (6,063)
Zip Code	Absent	60%	45%	1,609 (8,205)
Zip Code	Present	96%	92%	376 (1,634)
Edit	Major	59%	45%	2,622 (10,029)
	Minor	70%	58%	828 (3,833)
	Unedited	81%	73%	688 (5,877)
Density^b (persons/km²)	Rural, 0–221	65%	54%	2,069 (8,280)
	Suburban, 222–920	79%	71%	566 (6,172)
	Urban, ≥ 920	74%	60%	485 (2,319)
Datum^c	Unknown	60%	43%	1,600 (8,612)
	NAD27	64%	51%	1,475 (6,619)
	NAD83 or WGS84	87%	81%	590 (3,961)
Match Type	Centroid	100%	34%	5,331 (9,207)
	Street	100%	90%	607 (5,577)

^aSpherical distance in meters between criterion standard and vendor-assigned coordinates (mean [standard deviation]). ^bStratified at the 33^rd and 67^th percentiles. ^cOriginal datum of coordinates. NAD27 and NAD83 = North American Datum of 1927 and 1983. WGS84 = World Geodetic System of 1984.