Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.02466 -0.01647 -0.01154  0.00199  0.43471 

Coefficients:
                      Estimate Std. Error t value      Pr(>|t|)    
(Intercept)           0.011608   0.001912   6.070 0.00000000209 ***
xLow income           0.011006   0.004305   2.557      0.010777 *  
xLower middle income  0.013058   0.003462   3.772      0.000175 ***
xNA                  -0.008782   0.006595  -1.332      0.183413    
xUpper middle income  0.005542   0.003197   1.734      0.083440 .  
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.0334 on 707 degrees of freedom
Multiple R-squared:  0.02987,	Adjusted R-squared:  0.02438 
F-statistic: 5.442 on 4 and 707 DF,  p-value: 0.0002555