You'll hear people talk about the high cost of turnover, but when you try to press for the actual costs they don't really know. It seems like a mysterious thing that people talk about.

And it's true--the costs are largely hidden. It doesn't hit your profit and loss statement. It's not something in the budget. There are some hard costs, like the cost to post a position on a job board, or for specialized positions, the cost of a headhunter. But, even if you recruit strictly through word of mouth and employee referrals, there are costs to losing an employee. Here are the things you're paying for.

Lowered productivity. The person who left was doing something, right? And who is doing that job now that the position is vacant? No one? That's lost productivity right there. What if you just farm out the tasks to other people? Chances are, the most important tasks will get done, but other things will fall by the wayside.

Overworked remaining staff. Can you measure this in dollars? If your employees are exempt, their paychecks remain the same, so how is this a cost? Well, as they get stretched thin, their quality of work goes down as does their satisfaction and engagement. Which means that they are more and more likely to start looking for a new job and leave. And the longer they stay in their overworked roles, the harder it will be for you to regain their goodwill even after you've filled the vacancy.

Lost knowledge. A ton of people can do what your former employee did, but they don't have the specific knowledge she had. It's not just about putting numbers in a spreadsheet, writing code, or selling a product. It's about knowing the people, the traditions, the location of relevant information, what the boss likes and a million other things that come from working for a company for a long period of time. All that goes away when someone quits. And sometimes it's more than just general company knowledge. How many of your employees have their jobs documented well enough that someone could figure it out with their documentation? Do you have people cross trained? Does one person have control of the passwords?

Training costs. Paid training costs are obvious. If you have to pay $5,000 for a seminar to teach your new employee your complex internal computer systems, that's a cost noted on a spreadsheet. But, when there are no training classes to attend, there are still costs. Someone has to sit there and show him what to do. Someone has to double check work until the employee has proven himself. And that all takes the "trainer" away from her regular job. Which means you're paying two people to do one job. Costly.

Interviewing costs. If you have to pay travel expenses, that's costly. But if all your candidates are local, you still have to take the time to go through resumes, talk with numerous people, do formal interviews (which take an inordinate amount of time), talk with colleagues, and figure out who is the best employee.

Recruiters. I'm not talking headhunter fees (which are absolutely worth it for some positions), but rather the employee who has to find the candidates. In some business, you have dedicated HR or recruiting staff that takes care of this. They all get paid. And for smaller businesses, this task usually falls directly on the shoulders of the hiring manager--you know the one who is extra busy because he's down one person? That costs too.

What do all these costs add up to? Well how much? Estimates run as high as 150 percent of annual salary. Much less for lower level positions, but still significant enough to make retention a high priority for your business.

This doesn't mean you shouldn't fire problem employees. You should--because they aren't being productive and they encourage your good employees to quit. But, you should first try to counsel and coach and correct. And you should consider your pay scales for your good employees and give raises and bonuses when appropriate because it will cost you more to lose that good employee than the $5,000 raise you refused to give.