Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.13562 -0.03861 -0.01955  0.03017  0.28786 

Coefficients:
                      Estimate Std. Error t value      Pr(>|t|)    
(Intercept)           0.047908   0.009261   5.173 0.00000075881 ***
xLow income           0.089751   0.016612   5.403 0.00000026513 ***
xLower middle income  0.087737   0.014397   6.094 0.00000000956 ***
xNA                  -0.027684   0.066784  -0.415      0.679100    
xUpper middle income  0.051261   0.014173   3.617      0.000412 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.06614 on 144 degrees of freedom
Multiple R-squared:  0.2594,	Adjusted R-squared:  0.2388 
F-statistic: 12.61 on 4 and 144 DF,  p-value: 0.00000000805