Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.03692 -0.03271 -0.01423  0.00533  0.36604 

Coefficients:
                      Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.036922   0.002950  12.517 < 0.0000000000000002 ***
xLow income          -0.021978   0.006640  -3.310              0.00098 ***
xLower middle income -0.022688   0.005339  -4.249            0.0000243 ***
xNA                  -0.027217   0.010173  -2.675              0.00764 ** 
xUpper middle income -0.004201   0.004931  -0.852              0.39449    
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.05152 on 707 degrees of freedom
Multiple R-squared:  0.03871,	Adjusted R-squared:  0.03328 
F-statistic: 7.118 on 4 and 707 DF,  p-value: 0.00001274