Call:
lm(formula = y ~ x)

Residuals:
      Min        1Q    Median        3Q       Max 
-0.056458 -0.019706 -0.007644  0.007128  0.259166 

Coefficients:
                      Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.007654   0.002260   3.386             0.000748 ***
xLow income           0.036422   0.005088   7.158     0.00000000000205 ***
xLower middle income  0.048806   0.004091  11.929 < 0.0000000000000002 ***
xNA                  -0.002275   0.007795  -0.292             0.770468    
xUpper middle income  0.019646   0.003778   5.200     0.00000026185121 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.03948 on 707 degrees of freedom
Multiple R-squared:  0.1929,	Adjusted R-squared:  0.1883 
F-statistic: 42.24 on 4 and 707 DF,  p-value: < 0.00000000000000022