On some occasions of market fluctuations, fund managers will look at reducing some exposures. They may want to do this when they are pre-occupied elsewhere and need a short respite. If they close their positions it could prove expensive. An alternative is an overlay hedge which can be both less expensive and more efficient. This is done by adding off-setting derivatives, which will not off-set unwanted exposures but will help achieve a global hedge. This can be used only briefly during a market crisis where the correlation between market factors tend to increase.