Call:
lm(formula = y ~ x)

Residuals:
      Min        1Q    Median        3Q       Max 
-0.029638 -0.014656 -0.007912  0.001107  0.188051 

Coefficients:
                      Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.029639   0.001849  16.032 < 0.0000000000000002 ***
xLow income          -0.027194   0.004161  -6.535       0.000000000122 ***
xLower middle income -0.021713   0.003346  -6.489       0.000000000163 ***
xNA                  -0.022138   0.006375  -3.472             0.000547 ***
xUpper middle income -0.014980   0.003090  -4.847       0.000001538409 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.03229 on 707 degrees of freedom
Multiple R-squared:  0.09571,	Adjusted R-squared:  0.0906 
F-statistic: 18.71 on 4 and 707 DF,  p-value: 0.00000000000001247