Perps the best pmf in all of crypto… In 1992, Robert Shiller proposed perpetual futures, alongside a method for generating asset-price indices using hedonic regression, accounting for unmeasured qualities by adding dummy variables that represent elements of the index, indicating the unique quality of each element, a form of repeated measures design. This was intended to permit the creation of derivatives markets for illiquid, infrequently-priced assets, such as single-family homes, as well as untraded indices and flows of income, such as labour costs or the consumer price index.