Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.05457 -0.02458 -0.01235  0.00669  0.34885 

Coefficients:
                      Estimate Std. Error t value Pr(>|t|)    
(Intercept)           0.012362   0.006607   1.871   0.0634 .  
xLow income           0.042208   0.011850   3.562   0.0005 ***
xLower middle income  0.028002   0.010270   2.726   0.0072 ** 
xNA                  -0.012346   0.047641  -0.259   0.7959    
xUpper middle income  0.012465   0.010111   1.233   0.2197    
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.04718 on 144 degrees of freedom
Multiple R-squared:  0.09919,	Adjusted R-squared:  0.07417 
F-statistic: 3.964 on 4 and 144 DF,  p-value: 0.004408