Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.10630 -0.03894 -0.02560  0.04089  0.24755 

Coefficients:
                      Estimate Std. Error t value   Pr(>|t|)    
(Intercept)           0.038966   0.009823   3.967   0.000114 ***
xLow income           0.067392   0.017619   3.825   0.000194 ***
xLower middle income  0.076110   0.015270   4.984 0.00000176 ***
xNA                  -0.038932   0.070833  -0.550   0.583422    
xUpper middle income  0.062365   0.015033   4.149 0.00005694 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.07015 on 144 degrees of freedom
Multiple R-squared:  0.1917,	Adjusted R-squared:  0.1693 
F-statistic:  8.54 on 4 and 144 DF,  p-value: 0.000003265