Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.04258 -0.03913 -0.01894 -0.00572  0.67482 

Coefficients:
                      Estimate Std. Error t value        Pr(>|t|)    
(Intercept)           0.039139   0.005522   7.088 0.0000000000033 ***
xLow income          -0.033411   0.012429  -2.688         0.00736 ** 
xLower middle income  0.003442   0.009995   0.344         0.73062    
xNA                  -0.027568   0.019043  -1.448         0.14815    
xUpper middle income -0.020199   0.009230  -2.188         0.02897 *  
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.09644 on 707 degrees of freedom
Multiple R-squared:  0.01808,	Adjusted R-squared:  0.01253 
F-statistic: 3.255 on 4 and 707 DF,  p-value: 0.01167