Whisky fans, look away now; the world is facing a shortage of a single malt Scotch. A CNN report says demand for the Scottish "nectar" is so high distilleries can't keep up."The shortage of old and rare single malt. has started, and it's going to get worse," said Rickesh Kishnani, who launched the world's first whisky investment fund.Global single malt sales rose by 159% between 2004 and 2014, said the Scotch Whisky Association.Many new markets have a growing thirst for the drink - particularly Asia, which now consumes one-fifth of all exports. Experts say the shortage could last between 10 and 15 years and that it will push up prices.The Investment Grade Scotch Whisky Index, which tracks the value of high-end whiskies, increased by 14% last year.Scotland is not the only whisky-producing nation struggling to keep up with demand: US bourbon whiskey- makers face similar problems. ..