Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.01098 -0.00674 -0.00585  0.00076  0.48308 

Coefficients:
                      Estimate Std. Error t value Pr(>|t|)    
(Intercept)           0.005906   0.001554   3.800 0.000157 ***
xLow income           0.005008   0.003499   1.432 0.152716    
xLower middle income  0.005081   0.002813   1.806 0.071336 .  
xNA                  -0.003919   0.005360  -0.731 0.464992    
xUpper middle income  0.003724   0.002598   1.433 0.152191    
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.02714 on 707 degrees of freedom
Multiple R-squared:  0.008796,	Adjusted R-squared:  0.003188 
F-statistic: 1.568 on 4 and 707 DF,  p-value: 0.1809