Call:
lm(formula = y ~ x)

Residuals:
      Min        1Q    Median        3Q       Max 
-0.015206 -0.010581 -0.004297 -0.000360  0.196436 

Coefficients:
                      Estimate Std. Error t value      Pr(>|t|)    
(Intercept)           0.004303   0.001076   4.000 0.00007011118 ***
xLow income           0.006381   0.002422   2.635       0.00860 ** 
xLower middle income  0.006337   0.001947   3.254       0.00119 ** 
xNA                  -0.003932   0.003710  -1.060       0.28966    
xUpper middle income  0.010904   0.001798   6.063 0.00000000217 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.01879 on 707 degrees of freedom
Multiple R-squared:  0.05965,	Adjusted R-squared:  0.05433 
F-statistic: 11.21 on 4 and 707 DF,  p-value: 0.00000000799