Call:
lm(formula = y ~ x)

Residuals:
      Min        1Q    Median        3Q       Max 
-0.157262 -0.052300 -0.001433  0.062608  0.273222 

Coefficients:
                     Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.20540    0.01046  19.637 < 0.0000000000000002 ***
xLow income          -0.14294    0.01876  -7.619   0.0000000000031317 ***
xLower middle income -0.13730    0.01626  -8.444   0.0000000000000302 ***
xNA                   0.06261    0.07543   0.830                0.408    
xUpper middle income -0.08534    0.01601  -5.331   0.0000003685331141 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.0747 on 144 degrees of freedom
Multiple R-squared:  0.4087,	Adjusted R-squared:  0.3923 
F-statistic: 24.88 on 4 and 144 DF,  p-value: 0.000000000000001129