What is Window Dressing?
Window dressing occurs when fund managers sell poorly performing holdings and buy recent winners just before quarter-end or year-end reporting dates. Since reports show holdings at a point in time, the portfolio appears to have owned the best-performing stocks all along. The embarrassing losers disappear from the record, replaced by names investors recognize as winners.
Price Patterns That Tend to Appear Around Period-Ends
In Japan, most institutional investors close their books at the end of March (full-year results) and the end of September (interim results), so around those dates the market sometimes shows price moves that are attributed to window dressing. Two patterns are typical. The first is that popular, large-cap names that have already risen during the period get bought further and stay firm into the period-end, because buying that improves the look of the holdings list is easy to justify. The second is that selling pressure builds on underperforming names just before the period-end, then disappears once the new period starts, allowing those names to rebound. That said, period-end price moves involve several forces at once - dividend record dates, institutional money flowing in and out, index reconstitutions - so no individual move can be explained by window dressing alone.
The Cost to Investors and the Real Harm
Window dressing harms investors in multiple ways. Unnecessary trading generates transaction costs borne by the fund. Reports misrepresent the actual investment strategy, making it impossible to evaluate the manager's true approach. Buying high-priced winners and selling beaten-down losers at quarter-end is the opposite of sound investing and can drag on performance. There is indirect harm for individual investors too: misreading a period-end price move as a change in a company's underlying strength and buying at the top, or trusting the holdings list in the report and forming a mistaken picture of what the fund actually owns. When prices move sharply right around a period-end, it pays to first ask whether the cause is simply the supply and demand peculiar to reporting season.
How to Detect It
Window dressing is hard to detect with certainty, but there are clues. High portfolio turnover rates may indicate window dressing among other excessive trading. Compare the period-end holdings with the fund's stated strategy, and check whether those holdings are consistent with the returns actually earned during the period. If a fund underperformed during the period but its period-end holdings list is filled with that period's winners, there is room to suspect a swap made just before the close. The most reliable defense is choosing index funds, which have no incentive to window dress because they simply hold the index constituents.