Call:
lm(formula = y ~ x)

Residuals:
      Min        1Q    Median        3Q       Max 
-0.074292 -0.023493 -0.003356  0.014241  0.111628 

Coefficients:
                      Estimate Std. Error t value        Pr(>|t|)    
(Intercept)           0.031530   0.004758   6.626 0.0000000006401 ***
xLow income           0.061463   0.008535   7.201 0.0000000000305 ***
xLower middle income  0.024992   0.007397   3.379        0.000937 ***
xNA                  -0.003356   0.034312  -0.098        0.922227    
xUpper middle income  0.011647   0.007282   1.599        0.111910    
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.03398 on 144 degrees of freedom
Multiple R-squared:  0.277,	Adjusted R-squared:  0.2569 
F-statistic: 13.79 on 4 and 144 DF,  p-value: 0.000000001516