Lot's of things can be observed. Conclusion of correlation or rather causation is purely speculative however.
What I'm repeating and will be repeating is that such unethical methods like DRM have no place in any decent business. And they don't help sales of course. All they help are some crooks who want more control over the market or technology (DCMA-1201 and similar laws is their leverage on top of DRM).
> Can you point to any studies on this subject please?
I said "have been observed" and I gave three examples of games where DRM correlated with strong sales.
You are still repeating "There are studies proving the inverse" without ever referencing them.