Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.55344 -0.09504  0.01081  0.15803  0.38413 

Coefficients:
                     Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.62648    0.02662  23.530 < 0.0000000000000002 ***
xLow income          -0.25376    0.04776  -5.314        0.00000040006 ***
xLower middle income -0.26987    0.04139  -6.520        0.00000000111 ***
xNA                   0.15803    0.19199   0.823              0.41179    
xUpper middle income -0.13317    0.04075  -3.268              0.00135 ** 
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.1901 on 144 degrees of freedom
Multiple R-squared:  0.2769,	Adjusted R-squared:  0.2569 
F-statistic: 13.79 on 4 and 144 DF,  p-value: 0.000000001519