Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.06989 -0.01691 -0.01150  0.01858  0.13691 

Coefficients:
                      Estimate Std. Error t value      Pr(>|t|)    
(Intercept)           0.016922   0.005147   3.287       0.00127 ** 
xLow income           0.052991   0.009233   5.739 0.00000005416 ***
xLower middle income  0.050674   0.008002   6.333 0.00000000289 ***
xNA                  -0.016905   0.037119  -0.455       0.64948    
xUpper middle income  0.018249   0.007878   2.317       0.02194 *  
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.03676 on 144 degrees of freedom
Multiple R-squared:  0.2838,	Adjusted R-squared:  0.2639 
F-statistic: 14.27 on 4 and 144 DF,  p-value: 0.0000000007818