Fortunately not very much.
My clients are usually older, and exercise is not optional for them. Quite a few of them would have great difficulty working out on their own. Older clients are also often more insulated from the ups and downs of the market.
I have not change my rates; however, I also did not increase them. I had a few clients who dropped the frequency of their training with me.
What I have done to be more competitive was to widen my knowledge base and include more certifications in different modalities. The one that had the greatest positive impact was becoming a MELT instructor.