In the paper Park is partial to the 200-day moving average as the longer-term moving average, and he tests a variety of short-term averages ranging from 1 to 50 days.  It should come as no surprise that they all work!  In fact, they tend to work better than simple price-return based factors.  That didn’t come as a huge surprise to us, but only because we have been tracking a similar factor for several years that uses two moving averages.  What has always surprised me is how well that factor does when compared to other calculation methods over time.