Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.04762 -0.01988 -0.01173  0.00224  0.53976 

Coefficients:
                      Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.021109   0.002482   8.505 < 0.0000000000000002 ***
xLow income          -0.001221   0.005587  -0.219              0.82709    
xLower middle income -0.007347   0.004492  -1.636              0.10239    
xNA                   0.026521   0.008559   3.098              0.00202 ** 
xUpper middle income -0.001050   0.004149  -0.253              0.80031    
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.04335 on 707 degrees of freedom
Multiple R-squared:  0.01982,	Adjusted R-squared:  0.01427 
F-statistic: 3.574 on 4 and 707 DF,  p-value: 0.006764