Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.16368 -0.04488 -0.01641  0.03599  0.27965 

Coefficients:
                     Estimate Std. Error t value       Pr(>|t|)    
(Intercept)           0.05820    0.01092   5.330 0.000000371637 ***
xLow income           0.13365    0.01959   6.823 0.000000000229 ***
xLower middle income  0.09348    0.01698   5.507 0.000000163474 ***
xNA                  -0.01641    0.07874  -0.208         0.8352    
xUpper middle income  0.03212    0.01671   1.922         0.0566 .  
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.07798 on 144 degrees of freedom
Multiple R-squared:  0.2986,	Adjusted R-squared:  0.2791 
F-statistic: 15.32 on 4 and 144 DF,  p-value: 0.000000000183