As of 2015, Quiggin opposed Bitcoin, calling it a "delusion" that would lead to "environmental disaster" due to the "ever-increasing environmental damage from the electricity used in the 'mining' of Bitcoins" and that "The sooner this collective delusion comes to an end, the better." He also proposed that the value of Bitcoin was a refutation of the efficient market hypothesis: "The EMH states that the market value of an asset is equal to the best available estimate of the value of the services or income flows it will generate. In the case of a company stock, this is the discounted value of future earnings. Since Bitcoins do not generate any actual earnings, they must appreciate in value to ensure that people are willing to hold them. But an endless appreciation, with no flow of earnings or liquidation value, is precisely the kind of bubble the EMH says can’t happen."