Table 4.

Distribution of tracts by proportional error in estimate

	Exact	< 1%	1-2.99%	3-4.99%	5-10%	> 10%
Tracts with no change (n=49,757)
Areal interpolation (inc. water area)	0.140	0.680	0.111	0.024	0.018	0.025
Areal interpolation (land only)	0.145	0.695	0.110	0.023	0.017	0.010
NCDB	0.086	0.596	0.189	0.062	0.038	0.028
LTDB	0.157	0.699	0.098	0.021	0.015	0.010
NHGIS	0.160	0.700	0.095	0.020	0.015	0.010
Many to one tracts (n=981)
Areal interpolation (inc. water area)	0.115	0.616	0.154	0.041	0.030	0.045
Areal interpolation (land only)	0.120	0.640	0.148	0.038	0.023	0.031
NCDB	0.037	0.412	0.301	0.119	0.080	0.052
LTDB	0.138	0.648	0.127	0.034	0.024	0.029
NHGIS	0.140	0.647	0.123	0.038	0.023	0.029
One to many tracts – no divided block (n=6,138)
Areal interpolation (inc. water area)	0.000	0.022	0.045	0.047	0.115	0.770
Areal interpolation (land only)	0.000	0.020	0.045	0.049	0.119	0.766
NCDB	0.000	0.022	0.046	0.048	0.115	0.770
LTDB	0.196	0.632	0.104	0.027	0.023	0.018
NHGIS	0.196	0.632	0.104	0.027	0.023	0.018
Many to many tracts – no divided block (n=2,279)
Areal interpolation (inc. water area)	0.004	0.129	0.171	0.095	0.130	0.472
Areal interpolation (land only)	0.004	0.132	0.172	0.098	0.134	0.459
NCDB	0.004	0.118	0.172	0.100	0.133	0.472
LTDB	0.221	0.592	0.104	0.032	0.025	0.026
NHGIS	0.221	0.592	0.104	0.032	0.025	0.026
One to many tracts – with divided block (n=6,307)
Areal interpolation (inc. water area)	0.001	0.020	0.039	0.038	0.079	0.823
Areal interpolation (land only)	0.001	0.020	0.040	0.039	0.084	0.816
NCDB	0.001	0.021	0.039	0.037	0.081	0.822
LTDB	0.055	0.563	0.183	0.060	0.062	0.076
NHGIS	0.062	0.613	0.162	0.052	0.048	0.063
Many to many tracts – with divided block (n=6,743)
Areal interpolation (inc. water area)	0.004	0.194	0.204	0.086	0.101	0.410
Areal interpolation (land only)	0.004	0.193	0.213	0.088	0.104	0.398
NCDB	0.005	0.183	0.198	0.092	0.108	0.415
LTDB	0.057	0.530	0.205	0.064	0.053	0.090
NHGIS	0.066	0.595	0.175	0.050	0.042	0.073