Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.18228 -0.04223 -0.02883  0.03305  0.42221 

Coefficients:
                     Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.19071    0.01212  15.737 < 0.0000000000000002 ***
xLow income          -0.11526    0.02174  -5.302          0.000000422 ***
xLower middle income -0.10120    0.01884  -5.372          0.000000306 ***
xNA                  -0.03731    0.08739  -0.427                 0.67    
xUpper middle income -0.08290    0.01855  -4.470          0.000015733 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.08655 on 144 degrees of freedom
Multiple R-squared:  0.2361,	Adjusted R-squared:  0.2149 
F-statistic: 11.13 on 4 and 144 DF,  p-value: 0.00000006803