Millennials are notorious for switching jobs on the fly.

But they may want to think twice about bolting out the door too soon because they're leaving money on the table.

To see the biggest income increase you might want to work at your job at least three to five years before switching. Income for this group goes up the most -- 8.3% on average -- according to ADP, which analyzes payroll data.

"With three to five years (of experience), employees are marketable but not married to their current job," says Ahu Yildirmaz, head of ADP Research Institute.

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Employees who change jobs with less than three years under their belt typically only see a 2.7% pay bump.

With only a couple years experience, workers' skills aren't fully developed, making them less marketable than someone in the sweet spot of 3-5 years, says Yildirmaz. But after five years, workers tend to be more tied to their company and are climbing the leadership ranks.

That's why, once they cross the five-year threshold, their pay rises slightly less: 6%. And after 10 years, job switchers only see an increase of 2.2%.

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Americans are certainly feeling more confident about finding a job. Since September, the number of unemployed people who have restarted their job hunting process has risen.

On top of that, Americans are quitting their jobs more often now. That may sound like a bad thing, but an increasing rate of workers feel they can go elsewhere to find better work. During the recession, people held on to whatever jobs they had and the quit rate fell to 1.3%. It's slowly climbed up to 2.1% now, about where it was before the recession started.

Wages too are growing in recent months but it's still low and it's been anemic for many Americans during the economic recovery. Paltry wage growth is a key reason why many folks feel left out of the America's economic comeback.

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But with unemployment at a low 5%, wage growth could be coming around the corner, some experts say.

"We believe now that the labor market is hitting a turning point," says Yildirmaz. Employers "are keen on retaining their experienced workers."