Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.05361 -0.01854 -0.01128  0.00627  0.56331 

Coefficients:
                      Estimate Std. Error t value       Pr(>|t|)    
(Intercept)           0.018543   0.003198   5.798 0.000000010141 ***
xLow income           0.015987   0.007199   2.221         0.0267 *  
xLower middle income  0.031712   0.005789   5.478 0.000000059874 ***
xNA                  -0.014312   0.011030  -1.298         0.1948    
xUpper middle income  0.035072   0.005346   6.560 0.000000000104 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.05586 on 707 degrees of freedom
Multiple R-squared:  0.08257,	Adjusted R-squared:  0.07738 
F-statistic: 15.91 on 4 and 707 DF,  p-value: 0.000000000001777