[Harv72b]

You are going to need to make some adjustments to your game every time you move up a level; how your win rate is affected is just a question of how well you adapt.

It's been a while since I played .50/1 (at least, seriously), but I do know that 1/2 can be a difficult level to adjust to, particularly when the site is offering a bonus. A lot of part/time players just chase bonuses, and 1/2 is the level that many of them use to get their raked hands requirement; while these players are not world class pros, they are better (mostly just tighter) than the average Party donk.

You also have to take sample size into account. If you only played 5k or 10k hands at .50/1, then the 5 BB/100 could be partially a result of running well or running into a lot of really bad opponents. If you've only played a few thousand hands of 1/2, the lower win rate is statistically insignificant--cold cards, lucky suckouts, and just the period of adjustment to the new level can easily explain the difference over such a small amount of hands. From a mathematical standpoint, you literally need hundreds of thousands of hands at a given level before you can determine your true win rate with any degree of certainty; before that point you can make a general estimate (5 BB/100 over 10k hands almost definitely shows that you're a winning player, but your true win rate could be several BB/100 higher or lower).

I haven't had a big drop in my win rate as a result of moving up to new levels thus far, but I have had pretty big swings just based on simple variance. It is not at all uncommon to suffer through streaks involving tens of thousands of hands where you're winning at a much lower rate than usual (or even losing). This is regardless of how good a player you are.