There is an article on SecurityFocus from The Register discussing that if software piracy could be cut or stopped it would jumpstart the sluggish global economy.

IDC analysts estimate that reducing this figure to a third (30 per cent) could lead to the creation of 1.5 million new jobs, increase economic growth by $400bn and generate $64bn in new taxes.

Full Article
I am sure that if piracy were cut there would be an increase in spending, but statistics have a habit of serving their master and representing what the authors want them to.

When I have used "pirated" software it has almost always been to dabble with some technology that I wouldn't otherwise get to play with. For instance, if I download and install a pirated Microsoft Exchange I get to familiarize myself with the software and become proficient in configuring and administering it.

If I was somehow blocked from getting a pirated copy it does not mean that it would spur the economy. I just wouldn't use it. I have no real need for Exchange and can't afford to buy Exchange for my little 3 computer home network. In my opinion, piracy in this form actually helps the industry because it makes me into a product evangelist and gives me the skills needed to administer this in the real world.

For most instances, there are time-lapsed trial versions so you don't need a "pirate" copy, but my point is that many people who are using pirated software would not run out and buy a legitimate version if they couldn't get the pirated copy. They would either do without or find some other freeware / public domain alternative.