What do IT staff, mechanics, and laborers all have in common? They're among the 10 hardest job titles to fill nationally this year, according to a new study.IT talent ranked 9th (behind laborers but ahead of production operators) as the hardest job set to fill, according to a recent survey by staffing firm Manpower of 2,000 U.S. employers ranging from small to large companies.

What makes IT jobs so hard to fill these days?

"Everything is super-specialized, sub-specialized," says Tom Christ, lead IT business development manager for Manpower's Chicago region.

Prospective employers aren't just trying to find hot skills in products or technologies like Microsoft .Net or SharePoint, "they're zeroing in on very specific expertise, knowledge," he says.

"A bank isn't just looking for someone with .Net experience in the banking industry, it's looking for someone with treasury experience, too," he says. And with the economy being tight, employers don't have a lot of leeway in developing bench strength.

"Many companies don't have the manpower or time to wait getting people trained, they're wanting very specialized skills from day one," he says.

Here's the full list of Manpower's "10 Hardest Jobs to Fill"

1. Engineers 2. Machinists/Machine operators (10)* 3. Skilled trades 4. Technicians (4) 5. Sales representatives (1) 6. Accounting and finance staff (8) 7. Mechanics (3) 8. Laborers (9) 9. IT staff 10. Production operators

(*Represents ranking in Manpower's 2007 "10 Hardest Jobs to Fill" list.)

Other hard-to-fill jobs under the general "IT staff" banner include those requiring skills related to GPS, wireless, embedded software engineering, Java development, quality and assurance, and data warehousing, says Christ.

But again, having those skills isn't enough. Vertical industry and, in many cases, specific business unit expertise are what's being sought by many employers, he says.

"Everyone is being pretty selective," he says.

That probably explains why so many employers are supposedly having such a hard time filling those jobs.

What sort of talent is your IT organization having a hard time finding? (And are you being just a wee bit too picky, too?)