Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.11844 -0.03039 -0.01805  0.02656  0.35416 

Coefficients:
                      Estimate Std. Error t value      Pr(>|t|)    
(Intercept)           0.028007   0.009112   3.074       0.00253 ** 
xLow income           0.103686   0.016344   6.344 0.00000000273 ***
xLower middle income  0.082533   0.014165   5.826 0.00000003557 ***
xNA                  -0.018052   0.065708  -0.275       0.78391    
xUpper middle income  0.057156   0.013945   4.099 0.00006912438 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.06507 on 144 degrees of freedom
Multiple R-squared:  0.2811,	Adjusted R-squared:  0.2611 
F-statistic: 14.08 on 4 and 144 DF,  p-value: 0.000000001016