The world had found a new appreciation for the single malt. People around the globe are going through the aged whiskey so fast, distilleries can't keep up anymore.

The demand for aged whiskey, bourbon, scotch, even the Japanese brands has increased explosively in the recent years. Holding on to an old bottle can net a very handsome profit. People are not only enjoying a casual sip or two; they are also investing in these aged spirits.

Since the whiskey index was first set in place six years ago, CNN reports that the aged single malts has risen in value by more than 660%. People are investing serious money on these bottles and prices can reach exorbitant amounts. The world's most expensive bottle, the rare Macallan "M" whiskey, sold for $628,205 at an auction in Hong Kong on January of 2014.

Stephen Norman of Whisky Corporation told CNN Money "Whiskey as an investment is being driven by an escalating international demand, combined with an ever-decreasing supply of rare and aged single malt."

According to Rickesh Kishnani, the man who manages the world's only whiskey investment fund "The shortage of old and rare single malt... has already started, and it's going to get worse."

Whiskey, scotch, bourbon, are spirits distilled from grain such as rice, barley, or corn. They are mashed, distilled, and then aged in oak barrels. Top dollar bottles are aged ten to twenty years, and sometimes even for longer periods.

CNN reports that the problem is mainly caused by the system employed in producing these spirits. The age-labeled spirits are intended to be a limited commodity because producers only make a set amount each year without really knowing what demand will be like by the time they hit venerable ages. Although distilleries are increasing their capacity but the shortage is projected to last another ten to fifteen years from now.