If you're a numbers person, you will be interested in the graph above. It shows my side-to-side tap test scores over a period of nearly 8 years (from about 7.4 to 15.1 years post diagnosis).
In my version of the side-to-side tap test, using just the index finger on your left hand you type first q then p as many times as possible in a 30 second period. You then repeat with your right hand. A high score is good.
I have only included those tests taken at least 10 hours after the last medication (n=304). This should be long enough for most of the effects of the PD drugs to have ended. This is, therefore, an "off" test.
For me the left hand score is almost always higher than the right hand score. (My left hand is dominant, and is the least affected by PD.) The trend of both has been gently increasing (good) over the years, but I put this down mainly to a learning effect. Unfortunately, in the last 20 readings or so there appears to be a decrease of the scores.
John