Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.05000 -0.04947 -0.00219 -0.00070  0.58964 

Coefficients:
                      Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.050003   0.004422  11.308 < 0.0000000000000002 ***
xLow income          -0.049296   0.009953  -4.953       0.000000916311 ***
xLower middle income -0.047833   0.008004  -5.976       0.000000003616 ***
xNA                  -0.047810   0.015249  -3.135              0.00179 ** 
xUpper middle income -0.047775   0.007391  -6.464       0.000000000191 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.07722 on 707 degrees of freedom
Multiple R-squared:  0.08727,	Adjusted R-squared:  0.0821 
F-statistic:  16.9 on 4 and 707 DF,  p-value: 0.0000000000003053