PTTAX *looks* like it had a big drop on both 12-12-12 and 12-27-12. These were both income distribution dates. If you look at your account you will probably see that the *income distribution* may not have shown up in actual cash but rather you acquired additional shares of PTTAX. It *looks bad* on a price chart and can interfere with comparative relative strength calculations but in reality nothing really changed much. The income distribution (dividend) gets subtracted from the daily price data and you'll have to add it back in manually. With mutual funds these distributions usually occur once a year and since the amount distributed is larger in a relative sense than, say when its distributed monthly or quarterly, the price drop looks more dramatic.