3. Calculate conumer surplus and profit under a uniform price and under thirddegree price discrimination. Compare the two situations and comment on the result.
Answer:
Under uniform price, consumer surplus in each market is
\[
\operatorname{CS}_{A}^{*}=\frac{1}{2}\left(1-p^{*}\right)^{2}=\frac{25}{128} \text { and } \quad \text { CS }_{i}^{*}=\frac{1}{2}\left(\frac{1}{2}-p_{i}^{*}\right)^{2}=\frac{1}{128}
\]
Hence, overall consumer surplus is
\[
C S^{*}=C S_{A}^{*}+C S_{B}^{*}=\frac{25}{128}+\frac{1}{128}=\frac{26}{128}=0.2
\]
- With price discrimination, consumer surplus in each market is
\[
C S_{A}^{*}=\left(1-p_{A}^{*}\right)^{2} / 2=\frac{1}{8} \text { and } C S_{B}^{\prime \prime}=\left(\frac{1}{2}-p_{B}^{* *}\right)^{2} / 2=\frac{1}{32}
\]
Hence, overall cosnumer surplus is
\[
C S^{* *}=C S_{A}^{* *}+C S_{a}^{* *}=\frac{1}{8}+\frac{1}{32}=\frac{5}{32}=0.156
\]
- Thus, under price discrimination consumer surplus is lower than with uniform price.
Under aniform price, profit is
\[
\pi^{*}=p^{*}\left(1-p^{*}+1 / 2-p^{*}\right)=\frac{9}{32}=0.28
\]
With price discrimination, profit is
\[
\pi^{* *}=p_{A}^{* *}\left(1-p_{A}^{*}\right)+p_{B}^{*}\left(1 / 2-p_{B}^{* *}\right)=\frac{5}{16}=0.31
\]
Thus, under price discrimination profit is higher than with uniform price.