Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.25476 -0.05708 -0.03857  0.06096  0.38796 

Coefficients:
                     Estimate Std. Error t value         Pr(>|t|)    
(Intercept)           0.07732    0.01510   5.121 0.00000095899152 ***
xLow income           0.15706    0.02708   5.799 0.00000004065591 ***
xLower middle income  0.17748    0.02347   7.561 0.00000000000431 ***
xNA                  -0.05708    0.10889  -0.524            0.601    
xUpper middle income  0.10257    0.02311   4.439 0.00001787679009 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.1078 on 144 degrees of freedom
Multiple R-squared:  0.3283,	Adjusted R-squared:  0.3096 
F-statistic: 17.59 on 4 and 144 DF,  p-value: 0.000000000008884