Pirating isn't stealing, it's sharing! And sharing is caring!
But seriously,
Does Piracy Cause Economic Harm? How To Think About Economic Frontiers - Forbes
I personally think this issue is one of the biggest can of worms our society has seen on an economic front, and it's virtually impossible to quantify the various effects it has had. The fact is that the digital age really changed everything. There is a positive and negative side to piracy, along with a grey area in between. To cover all three angle in one example:
If someone pirates a movie and likes it, they could blog or post wherever about it and influence x number of people to buy that movie who wouldn't have done so prior. If someone pirates a movie and hates it, they could likewise influence x number of people to not buy it. But since people's opinions on entertainment are often based purely on a matter of personal taste, we have our grey area.
Would the results be the same if there was no piracy? It could be a wash. People, whenever able, will buy what they enjoy when it becomes available at what they'd consider a fair price point. Unless they're soulless bastards.
A society with piracy is really the truest definition of a free market society, and either help or hinder its progress and the quality of content available to it. Overall piracy could be considered an effective measure of quality control, because it's largely unbiased. What's worse; someone pirating a digital copy of something, or a corporation trying to convince people through massive marketing efforts that something is "worth their money", when perhaps it really isn't.
Like pretty much anything, education is key. The rest will follow hopefully for the better.