Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.11970 -0.04878 -0.02778 -0.00528  0.66373 

Coefficients:
                      Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.050996   0.006047   8.433 < 0.0000000000000002 ***
xLow income          -0.048312   0.013612  -3.549             0.000412 ***
xLower middle income -0.042036   0.010945  -3.841             0.000134 ***
xNA                   0.068707   0.020854   3.295             0.001035 ** 
xUpper middle income -0.020965   0.010108  -2.074             0.038436 *  
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.1056 on 707 degrees of freedom
Multiple R-squared:  0.05421,	Adjusted R-squared:  0.04886 
F-statistic: 10.13 on 4 and 707 DF,  p-value: 0.00000005595