Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.13925 -0.04531 -0.02747 -0.00683  0.47552 

Coefficients:
                      Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.027482   0.006752   4.070            0.0000523 ***
xLow income          -0.018708   0.015199  -1.231                0.219    
xLower middle income  0.017846   0.012222   1.460                0.145    
xNA                  -0.027412   0.023286  -1.177                0.240    
xUpper middle income  0.111765   0.011287   9.902 < 0.0000000000000002 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.1179 on 707 degrees of freedom
Multiple R-squared:  0.147,	Adjusted R-squared:  0.1422 
F-statistic: 30.47 on 4 and 707 DF,  p-value: < 0.00000000000000022