Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.05186 -0.02118 -0.01919  0.01451  0.23647 

Coefficients:
                      Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.021181   0.002518   8.412 0.000000000000000223 ***
xLow income           0.021814   0.005668   3.849             0.000129 ***
xLower middle income  0.030685   0.004558   6.733 0.000000000034491944 ***
xNA                  -0.007901   0.008684  -0.910             0.363200    
xUpper middle income  0.010771   0.004209   2.559             0.010701 *  
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.04398 on 707 degrees of freedom
Multiple R-squared:  0.07277,	Adjusted R-squared:  0.06752 
F-statistic: 13.87 on 4 and 707 DF,  p-value: 0.00000000006731