You may have been asking this question facetiously, but I am going to assume you are serious.
Here is a copy of the UPDRS (United Parkinson's Disease Rating Scale)
http://www.mdvu.org/library/ratingscales/pd/updrs.pdf

The Motor Skills might be the only "objective" portion of the test because you tap your fingers a certain number of times before assigning a numerical value. But even within that area of testing are questions such as:
"Facial expression"
0= Normal
1= Minimal hypomimia, could be normal "Poker Face"
3= Slight but definitelly abnormal diminutioon of facial aaexpressioon
3=Moderate hymimia; lips parted some of the time
4= Masked or fixed facies with severe or complete loss of facial expression; lips parted 1/4 inch or more.

So in reality, most of the testing that screens a person into a study, or measures their digression or improvement is . . . at best . . . subjective. And what is worse - this is how we are diagnosed!

Soo I think until we have a REAL test (blood test, x-ray, MRI, etc), then our PD diagnosis is highly subjective.
Peggy