Call:
lm(formula = y ~ x)

Residuals:
      Min        1Q    Median        3Q       Max 
-0.068669 -0.015472 -0.003184  0.001944  0.190316 

Coefficients:
                       Estimate Std. Error t value             Pr(>|t|)    
(Intercept)           0.0031907  0.0017281   1.846               0.0653 .  
xLow income           0.0654803  0.0038898  16.834 < 0.0000000000000002 ***
xLower middle income  0.0392174  0.0031278  12.538 < 0.0000000000000002 ***
xNA                  -0.0002962  0.0059595  -0.050               0.9604    
xUpper middle income  0.0143812  0.0028886   4.979          0.000000805 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.03018 on 707 degrees of freedom
Multiple R-squared:  0.3454,	Adjusted R-squared:  0.3417 
F-statistic: 93.26 on 4 and 707 DF,  p-value: < 0.00000000000000022