Reading the Letter to Partners of Buffett Partnership 06 Jul 1962

In the first half of 1962, the Dow declined 21.7% from 731.14 to 561.28 (including dividends received), where Buffett Partnership achieving minus 7.5%, different 14.2%.

If you are evaluating the performance of your investment manager, let's me borrow a quote from Buffett:

Investment performance must be judged over a period of time with such a period including both advancing and declining markets.