Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.01693 -0.01686 -0.00465 -0.00089  0.47024 

Coefficients:
                      Estimate Std. Error t value           Pr(>|t|)    
(Intercept)           0.016934   0.002198   7.705 0.0000000000000444 ***
xLow income          -0.016625   0.004947  -3.361           0.000820 ***
xLower middle income -0.016029   0.003978  -4.029 0.0000619994178972 ***
xNA                  -0.015716   0.007580  -2.074           0.038484 *  
xUpper middle income -0.012268   0.003674  -3.339           0.000884 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.03838 on 707 degrees of freedom
Multiple R-squared:  0.03558,	Adjusted R-squared:  0.03013 
F-statistic: 6.521 on 4 and 707 DF,  p-value: 0.0000372