Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.03910 -0.03901 -0.00941 -0.00361  0.45935 

Coefficients:
                      Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.039101   0.003329  11.745 < 0.0000000000000002 ***
xLow income          -0.030677   0.007494  -4.094          0.000047342 ***
xLower middle income -0.030440   0.006026  -5.052          0.000000558 ***
xNA                  -0.006553   0.011481  -0.571                0.568    
xUpper middle income -0.029626   0.005565  -5.324          0.000000137 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.05814 on 707 degrees of freedom
Multiple R-squared:  0.06134,	Adjusted R-squared:  0.05603 
F-statistic: 11.55 on 4 and 707 DF,  p-value: 0.000000004336