How does the prior years return impact future performance

In the following study I decided to analyze the walk forward performance of some highly liquid ETFs.  For this study the ETFs are divided into four buckets of performance over the prior year.   The buckets are as follows,  bucket1 (-50% to -25%),  bucket2 (-25% to 0%), bucket3 (0% to 25%),  bucket4 (25% to 50%).  The walk forward periods are 90, 120 and 252 days.   What is interesting is that the best walk-forward performance occurs when the prior year performance is in bucket1 (-50% to -25%). 

The 252 days walk-forward period performance is on average between 45% and 70% if the prior year was in bucket1.   Similarly in all cases if the average over the prior year was in bucket 4 (25% to 50%) in the next 90, 120, 252 walk forward periods the performance is negative.    The trading strategy would be load up  when the prior year is in bucket 1and short when the prior year is in bucket 4 .  Note also the the 252 day walk forward period is significantly better than both the 90 and 120 day periods.