Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.06616 -0.02378 -0.01720  0.01968  0.23725 

Coefficients:
                     Estimate Std. Error t value  Pr(>|t|)    
(Intercept)           0.02204    0.00692   3.185   0.00177 ** 
xLow income           0.01440    0.01241   1.160   0.24788    
xLower middle income  0.02544    0.01076   2.365   0.01939 *  
xNA                  -0.02203    0.04990  -0.441   0.65957    
xUpper middle income  0.04412    0.01059   4.166 0.0000533 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.04942 on 144 degrees of freedom
Multiple R-squared:  0.1157,	Adjusted R-squared:  0.09113 
F-statistic:  4.71 on 4 and 144 DF,  p-value: 0.001334