Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.03408 -0.03395 -0.00288 -0.00095  0.53061 

Coefficients:
                      Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.034078   0.003500   9.738 < 0.0000000000000002 ***
xLow income          -0.032547   0.007877  -4.132          0.000040305 ***
xLower middle income -0.033126   0.006334  -5.230          0.000000224 ***
xNA                  -0.034050   0.012068  -2.821              0.00491 ** 
xUpper middle income -0.031155   0.005850  -5.326          0.000000135 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.06112 on 707 degrees of freedom
Multiple R-squared:  0.06442,	Adjusted R-squared:  0.05913 
F-statistic: 12.17 on 4 and 707 DF,  p-value: 0.000000001422