Gold prices fall based on two things; economists learn both of these in Economics 101.

The first is that low demand puts downward pressure on prices. And secondly, oversupply in a market also forces prices down. That applies to gold, as it would in any other market or industry.
read more here http://www.dailyreckoning.com.au/the-real-reason-gold-prices-are-falling-cw/2015/07/30/