We have the same issue. Dramatic decrease for search impressions (any keyword changes can not fix it, though we have a lot of top5 positions for high volume keywords) and growth for browse impressions. As app units have approximately the same level, those impression dances causes the enormous growth of CR. It's already 3 months that Search CR keeps growing, due to the fact that Search impressions keep fall down while Search App Units as well as keyword positions stay stable. Normally, if we see the decline of Impressions we also see the decline of App Units, but not in this case. I would be trully happy if we had that kind of CR naturally, but right now this result don't seem right. Hope Apple will pay attention and fix it.