Not the zombies themselves, mind you.  I suspect that zombies spend very little cash.

But zombie things add $5 billion to the economy, according to the website 24/7 Wall Street.  They explain:

Think way beyond zombie movie ticket sales. Think about DVD sales, video games, comic books, novels, Halloween costumes, zombie walks, merchandise, conventions and even zombie art. Add to that all of the websites, homemade movies, Facebook sites, YouTube sites and other forms of "digital" zombies, not to mention music. And if you think the financial tab has been high so far, by the end of 2012 the tab is going to be far larger.

The breakdown?

• Movies: $2.5 billion.
• Video games: $2.5 billion.
• Comic books, magazines, TV: $50 million.
• Halloween costumes: $500 million over four years.
• Books: $100 million.
• Merchandise: $50 million.
• Conventions, events, walks: $10 million.
• Digital world: $10 million.
• Music: $10 million.
• Art: $10 million.