Call:
lm(formula = y ~ x)

Residuals:
      Min        1Q    Median        3Q       Max 
-0.077607 -0.011443 -0.001562 -0.001524  0.271907 

Coefficients:
                     Estimate Std. Error t value             Pr(>|t|)    
(Intercept)          0.001564   0.002475   0.632               0.5275    
xLow income          0.076045   0.005570  13.652 < 0.0000000000000002 ***
xLower middle income 0.032342   0.004479   7.221     0.00000000000134 ***
xNA                  0.001453   0.008534   0.170               0.8648    
xUpper middle income 0.009882   0.004136   2.389               0.0172 *  
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.04322 on 707 degrees of freedom
Multiple R-squared:  0.2309,	Adjusted R-squared:  0.2265 
F-statistic: 53.06 on 4 and 707 DF,  p-value: < 0.00000000000000022