71% of employees are missing out on a simple way to earn more money

One of the simplest ways to boost your earning potential is to ask for a raise, yet most people don't do it.

According to new research from recruiting software company Jobvite, "only 29 percent of job seekers negotiated their salary at their current or most recent job," meaning 71 percent of employees could be missing out on a fatter paycheck.

After all, negotiating works: 84 percent of those confident enough to ask for higher pay succeed in getting it, Jobvite reports. Plus, in about a fifth of cases, negotiators were rewarded with a significant pay increase of 11 to 20 percent.

But lots of people simply aren't comfortable asking for more money, Jobvite finds: 56 percent of men overall feel comfortable negotiating, versus only 38 percent of women.

Negotiation can be a tricky business, but not getting paid what you're worth could mean the difference between an average life and a rich one. As self-made millionaire Grant Sabatier says: "The number one thing that will dictate your future earning potential and get you to $1 million the fastest is how much money you are being paid today. Unfortunately, you probably aren't being paid what you are worth."

Sabatier recommends looking at the salary range for someone with your level of experience in your industry, which will help you understand what you're worth. Take that information to your boss and emphasize what you bring to the company, he says.

Of course, before sitting down with your boss, you'll want to prepare to prove your value and do mock negotiations over and over again. The more you practice and prepare ahead of time, the less likely you are to fumble through the actual negotiation.

And remember, it never hurts to ask, Sabatier tells CNBC: "A lot of people are ultimately afraid that people are going to say no, and so they undervalue themselves and they undervalue their services."

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