If $ 1 \minus{} y$ is used as an approximation to the value of $ \frac {1}{1 \plus{} y}$, $ |y| < 1$, the ratio of the error made to the correct value is:

$ \textbf{(A)}\ y \qquad \textbf{(B)}\ y^2 \qquad \textbf{(C)}\ \frac {1}{1 \plus{} y} \qquad \textbf{(D)}\ \frac {y}{1 \plus{} y} \qquad \textbf{(E)}\ \frac {y^2}{1 \plus{} y}\qquad$
1. We start with the given approximation \( 1 - y \) for the value of \( \frac{1}{1 + y} \) where \( |y| < 1 \).
2. The error in the approximation is given by the difference between the actual value and the approximate value:
   \[
   \text{Error} = \frac{1}{1 + y} - (1 - y)
   \]
3. Simplify the expression for the error:
   \[
   \text{Error} = \frac{1}{1 + y} - 1 + y
   \]
4. Combine the terms over a common denominator:
   \[
   \text{Error} = \frac{1 - (1 + y)(1 - y)}{1 + y} = \frac{1 - (1 - y^2)}{1 + y} = \frac{1 - 1 + y^2}{1 + y} = \frac{y^2}{1 + y}
   \]
5. The correct value is \( \frac{1}{1 + y} \).
6. The ratio of the error to the correct value is:
   \[
   \text{Ratio} = \frac{\text{Error}}{\text{Correct Value}} = \frac{\frac{y^2}{1 + y}}{\frac{1}{1 + y}} = y^2
   \]

The final answer is \( \boxed{y^2} \).