Piracy may not have much of an effect on huge corporations like EA, Blizzard, Universal Studios or Warner Bros - at least not right now - but it has pretty drastic effects on smaller publishers and self-published guys. There's pretty well-documented statistics from a number of indie devs who have collected data on how people are playing their game.
2DBoy released a game called World of Goo a few years ago and had a sale that allowed you to pay anything you wanted. In one week they sold 58,000 copies of the game, and about 16,000 of those went for $0.01. Another 16,000 sold for less than $2.00. That in itself is a bit of a sad statistic, but at least those people paid for the game, right? A little while later they revealed that through collecting data on how many different ip's were connecting to their servers at any given time and how many copies they'd sold, they estimated that their game had about a 90% piracy rate. Meaning that for every legit, bought game on their servers, there were 9 that had been pirated. If those people had paid even just one penny to the devs, they would have made an extra $5,000, and that's just in the first week. If those people had paid one dollar each, the devs would have made half a million dollars. And I'm just basing that on the one week of sales. I'm assuming that the number of sales when they released that statistic would have increased quite a bit.
The guys who made super meat boy have estimated similarly high piracy rates for their game, though not quite that high. Thing is, neither of these devs really give a shit because they know adding DRM to their game would just be a waste of time, and that piracy can lead to sales via popularity.
But the idea that piracy is some small statistic is quite wrong. There have been larger games with similar piracy rates. Quake 3 Arena was majorly pirated as well, at about two pirated copies to every legit copy on most servers. The reason they even started looking at the statistics for that one was because they noticed that the number of people who were playing the game at one time was higher than the number of copies of the game they had actually sold. That game sold in the millions, and there were at least twice as many millions of pirated copies.
Piracy has obvious effect on music. Back in 2000 or 2001 a couple of stores released some statistics that showed something like 60% drop in singles sales and 20% or so in album sales. Some of this might have been made up for in online sales via Amazon or sites like that, but I don't think mp3 sales had become a thing at that point, so it would have just been CD sales I think. I think Napster is the most likely cause of that sort of drop, tho. I feel pretty confident in assuming that there are kids out there now who have never paid a flat dime for a song in their lives.
And while movie studios are making a lot of money right now, ticket sales are dropping. I would not be surprised to learn that overall DVD sales have dropped by a significant number as well. 10-20% from five or ten years ago would not surprise me at all. I'm just taking a wild stab at that based on the spread of broadband over the last decade and the crazy growth in popularity of torrents. I would also not be surprised to learn that the piracy rate for DVD's is similar to that of games, though maybe not as high as it must be now for music.
The real problem is that the generation of kids out there right now are pretty much hard wired to torrent whatever the hell they want as a first option. The idea of actually buying software, movies, music or games is completely foreign to some of them. They're too young to get jobs, tho, so they don't have the sort of cash to drop on whatever they want. Right now the amount of money being lost isn't all that significant in most cases because that generation of kids hasn't reached the 'bread & butter' age where they have a bunch of disposable income to spend on going to shitty blockbusters and buying crappy pop music and generic shooter video games and all that other stuff that's marketed to the 16-25 crowd of people.
Wait ten years and compare sales statistics for 2012 and 2022.