Call:
lm(formula = y ~ x)

Residuals:
      Min        1Q    Median        3Q       Max 
-0.025771 -0.013111 -0.007023 -0.001216  0.266117 

Coefficients:
                     Estimate Std. Error t value      Pr(>|t|)    
(Intercept)          0.007029   0.001773   3.964 0.00008119524 ***
xLow income          0.005641   0.003991   1.413         0.158    
xLower middle income 0.018743   0.003210   5.840 0.00000000797 ***
xNA                  0.002317   0.006115   0.379         0.705    
xUpper middle income 0.015880   0.002964   5.358 0.00000011426 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.03097 on 707 degrees of freedom
Multiple R-squared:  0.06465,	Adjusted R-squared:  0.05936 
F-statistic: 12.22 on 4 and 707 DF,  p-value: 0.000000001309