Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.05227 -0.02245 -0.00949  0.00881  0.32451 

Coefficients:
                     Estimate Std. Error t value             Pr(>|t|)    
(Intercept)          0.009506   0.002686   3.539             0.000428 ***
xLow income          0.040709   0.006047   6.732      0.0000000000346 ***
xLower middle income 0.042770   0.004862   8.796 < 0.0000000000000002 ***
xNA                  0.008856   0.009264   0.956             0.339451    
xUpper middle income 0.030448   0.004490   6.781      0.0000000000253 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.04692 on 707 degrees of freedom
Multiple R-squared:  0.1363,	Adjusted R-squared:  0.1315 
F-statistic:  27.9 on 4 and 707 DF,  p-value: < 0.00000000000000022