Accuracy of commercial geocoding: assessment and implications

Table 3 Accuracy of geocodes assigned by the four vendors

Vendor	Match Rate			Concordance			ρ ^c
	Overall ^a	Street	Centroid ^b	Block Group	Tract	County
A	98%	79%	20%	77%	85%	99%	1809 (8790)
B	82%	78%	4%	83%	88%	99%	748 (4611)
C	81%	77%	4%	81%	87%	99%	704 (4418)
D	30%	30%	0%	97%	98%	100%	228 (884)

^aDue to rounding, may differ from the sum of street- and centroid-type match rates.
^bGeographic or delivery-weighted center of a statistical tabulation area, e.g. U.S. Census tract. ^cSpherical distance in meters between criterion standard and vendor-assigned coordinates (mean [standard deviation]).