Share tip services usually bodge performance in a number of ways. You can safely say they try to make their stats look as good as possible in order to get you to sign up. The bodges are easy.
The most common one is to use mid-prices rather than offer to bid. It is industry standard to do this and no-one wants to break ranks. I admit that when at t1ps the performance of Steve & I was calculated in this way. It gets compliance sign off, it is legal, everyone does it but it is completely misleading. It is not as if your poor readers get to buy and sell at the mid.
I know of penny stocks that trade at 1p-1.5p. Tip such a stock and see it go to 2.25-2.75p and the industry standard website will claim a 100% gain. The real gain is of course 50% - if you serve up only 10 or so tips a year that “fudge” allows you to boost your stated performance by 5 percentage points. But it is thoroughly misleading.
Steve & I admit to have sinned with the rest of the industry but we have repented and wish others would do the same
The second is to claim performance from one share commentator to promote your publication when he or she does not in fact write for it anymore. I note that Red Hot Penny Shares (a publication I was the founder editor of in 1998) has recently changed editor. Yet