Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.05817 -0.04085 -0.02734  0.01517  0.40604 

Coefficients:
                      Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.040858   0.003918  10.430 < 0.0000000000000002 ***
xLow income          -0.004262   0.008818  -0.483              0.62905    
xLower middle income  0.003819   0.007091   0.539              0.59033    
xNA                  -0.026983   0.013510  -1.997              0.04618 *  
xUpper middle income  0.017314   0.006548   2.644              0.00838 ** 
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.06842 on 707 degrees of freedom
Multiple R-squared:  0.01976,	Adjusted R-squared:  0.01421 
F-statistic: 3.563 on 4 and 707 DF,  p-value: 0.006894