Call:
lm(formula = y ~ x)

Residuals:
      Min        1Q    Median        3Q       Max 
-0.034947 -0.008952 -0.005953  0.005628  0.264825 

Coefficients:
                      Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.006589   0.001319   4.996       0.000000737331 ***
xLow income           0.028361   0.002968   9.554 < 0.0000000000000002 ***
xLower middle income  0.015651   0.002387   6.557       0.000000000106 ***
xNA                  -0.003713   0.004548  -0.817             0.414463    
xUpper middle income  0.007459   0.002204   3.384             0.000754 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.02303 on 707 degrees of freedom
Multiple R-squared:  0.1423,	Adjusted R-squared:  0.1374 
F-statistic: 29.32 on 4 and 707 DF,  p-value: < 0.00000000000000022