There are none. There are research prongs that will always be ambiguous.


First, there is the issue of sales lost: You need to know how a group of people (pirates) would have acted in the absence of piracy. How many of these people would have acquired and played the game legitimately? Would they have purchased the software legitimately if an illegitimate copy was not available to them? There really isn't a way to make a control group on this.

Second, there is the issue of network effects. You need to know the increase in popularity due to the network effect. How can you possibly know what the popularity would have been without a significant portion of the vocal, social community. Sometimes the presence of high piracy rates translates to a quality game that people will purchase but otherwise would have skipped. If the game is popular and people are talking about it, it must be good enough to purchase, so they do. Like above, there is no way to estimate the popularity of something under an alternate environment.

I'm sure there are more naturally ambiguous items.


There are other items that can be researched with less ambiguity. For example, you can do research to discover how many pirates purchased a legitimate copy of the game at a later date. You can do research to discover how many pirates downloaded but did not actually play the game, how many played but did not progress very far, or how many pirates played the game and later shouted its praises to the world.