Table 5.

Variance explained and factor loadings for supervised PCA, by tract.

Variable	Tract
	Factor 1	Factor 2
Over age 65	$-0.09$	0.84
Living alone	0.17	0.76
Living under poverty level	0.37	$-0.24$
Impervious surface (NLCD)	0.94	0.06
Nontree canopy (NLCD)	0.78	0.05
Nonvegetated including water (aerial)	0.84	0.10
Variance explaineda
Eigenvalue	2.30	1.36
% Variance explained	39.8	22.3

Note: NLCD, National Land Cover Database; PCA, principal components analysis.