Update : Oct. 29, 2012
An Inverse Indicator is an indicator calculated by multiplying the daily fluctuation rate of the underlying index (TOPIX, etc.) by a certain factor.
Inverse Indicators have price movements and returns that differ with those of regular indicators. The following is a specific explanation of the traits of the TOPIX Inverse (-1x) Indicator.
The graph below shows a case of TOPIX in decline. In such a case, the TOPIX Inverse (-1x) Index will have a daily fluctuation rate equal to -1x that of the underlying indicator.
However, if a period of 2 business days or longer (Base date to 2nd day) is examined, whereas TOPIX fell 14.5% (100 to 85.5), TOPIX Inverse (-1x) Index rose 15.5% (100 to 115.5), producing a result that is not exactly -1x the fluctuation rate of the underlying indicator.
In this way, it is possible to aim for returns during a declining market using an Inverse Indicator. However, when compared over a period of 2 business days or longer, the rate of increase may differ from the expected fluctuation rate (-1x the underlying indicator). The longer the period of investment, the greater the possibility for discrepancy between the fluctuation rates of the underlying indicator and the Inverse Indicator.

The following graph shows a case of TOPIX on the rise. In such a case, the TOPIX Inverse (-1x) Index will have a daily fluctuation rate that is -1x that of the underlying indicator.
However, just as in Example 1, if a period of 2 business days or longer is examined, whereas TOPIX rose 15.5% (100 to 115.5), TOPIX Inverse (-1x) Index fell 14.5% (100 to 85.5), producing a result not exactly -1x the fluctuation rate of the underlying indicator.
In this way, the Inverse Indicator produces a decline when the market is on the rise. However, when compared over a period of 2 business days or longer, the rate of decline may differ from the expected fluctuation rate (-1x the underlying indicator). The longer the period of investment, the greater the possibility for discrepancy between the fluctuation rates of the underlying indicator and the Inverse Indicator.

Finally, the following graph shows a case of the underlying indicator TOPIX experiencing a series of gains and losses. In such a case, the TOPIX Inverse (-1x) Indicator will again have a daily fluctuation rate that is -1x that of the underlying indicator.
However, though TOPIX has returned to the base date’s level by the 3rd day, the TOPIX Inverse (-1x) Index moved from 100 to 98.6, not recovering to the base date value due to its compounded movements.
In cases where the market’s direction is unclear and the underlying indicator repeatedly rises and falls, an Inverse Indicator’s performance will be gradually decreased compared to that of the underlying indicator due to the compounding effect.

Inverse Indicators are calculated to produce -1x the daily fluctuation rate of the underlying indicator, and thus profit and loss will be reversed.