Dropped?

A year ago the high for the day was $6.88 per bitcoin.  Today the low so far was $72.5.  Sounds like an increase of $65.62 (853.78%) to me.

Perhaps you just meant since the beginning of this year (2013)?  Lets see...
Jan.1 the high for the day was $13.56.  Nope that's an increase of $58.94 (334.66%).

Maybe you meant the past 24 hours?
24 hours ago the exchange rate was $71.5.  At the moment the rate is $78.  That's in increase of 9% over 24 hours.

Perhaps you are just choosing an arbitrary time in the past when it just happened to be higher and comparing it to a lower value?
In that case, I'd say it dropped because you chose a time in the past when the exchange rate was higher.