Call:
lm(formula = y ~ x)

Residuals:
      Min        1Q    Median        3Q       Max 
-0.019278 -0.011162 -0.006854  0.002469  0.217760 

Coefficients:
                      Estimate Std. Error t value     Pr(>|t|)    
(Intercept)           0.008306   0.001438   5.778 0.0000000114 ***
xLow income           0.008726   0.003236   2.696      0.00718 ** 
xLower middle income  0.010973   0.002602   4.217 0.0000280117 ***
xNA                  -0.004536   0.004958  -0.915      0.36056    
xUpper middle income  0.007708   0.002403   3.207      0.00140 ** 
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.02511 on 707 degrees of freedom
Multiple R-squared:  0.03705,	Adjusted R-squared:  0.0316 
F-statistic: 6.801 on 4 and 707 DF,  p-value: 0.00002253