It's very hard to say.
Many of the answers that say "Yes" here don't even bother measuring the effect that might be had from exposing people to new ideas, or the idea that there are parasitic industries. Consider the textbook industry. College textbooks are an additional onerous barrier to the success of poor students. Torrented college textbooks cheapen education and can give people the ability to learn.
Every person who listens to a song, watches a movie, reads a book, and doesn't pay for it, does deprive someone of money they would get, but they also grow and learn.
We don't even have the measurements to figure out how to rate that as a value, let alone to figure out its long term impacts.
What's clear is that digital piracy is a service issue. People are willing to pay in lots of instances, if they're being given a better product. Piracy is actually competition.