Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.13702 -0.06422 -0.02120  0.02428  0.55630 

Coefficients:
                     Estimate Std. Error t value             Pr(>|t|)    
(Intercept)          0.021208   0.006112   3.470             0.000552 ***
xLow income          0.115818   0.013757   8.419 < 0.0000000000000002 ***
xLower middle income 0.107500   0.011062   9.718 < 0.0000000000000002 ***
xNA                  0.054607   0.021077   2.591             0.009770 ** 
xUpper middle income 0.078666   0.010216   7.700   0.0000000000000459 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.1067 on 707 degrees of freedom
Multiple R-squared:  0.1711,	Adjusted R-squared:  0.1664 
F-statistic: 36.49 on 4 and 707 DF,  p-value: < 0.00000000000000022