Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.33745 -0.08391 -0.01185  0.13461  0.34540 

Coefficients:
                     Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.33746    0.02047  16.487 < 0.0000000000000002 ***
xLow income          -0.26868    0.03671  -7.318    0.000000000016224 ***
xLower middle income -0.25354    0.03182  -7.968    0.000000000000448 ***
xNA                   0.13461    0.14760   0.912                0.363    
xUpper middle income -0.17979    0.03132  -5.740    0.000000054095357 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.1462 on 144 degrees of freedom
Multiple R-squared:  0.3905,	Adjusted R-squared:  0.3736 
F-statistic: 23.07 on 4 and 144 DF,  p-value: 0.000000000000009594