Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.10831 -0.03681 -0.01369 -0.00644  0.54955 

Coefficients:
                      Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.036875   0.003774   9.772 < 0.0000000000000002 ***
xLow income          -0.030131   0.008494  -3.547             0.000415 ***
xLower middle income -0.029458   0.006830  -4.313         0.0000184201 ***
xNA                   0.071440   0.013014   5.489         0.0000000562 ***
xUpper middle income -0.021425   0.006308  -3.396             0.000721 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.06591 on 707 degrees of freedom
Multiple R-squared:  0.09405,	Adjusted R-squared:  0.08892 
F-statistic: 18.35 on 4 and 707 DF,  p-value: 0.00000000000002354