By the time your 50s roll around, you should be well on your way to building a retirement nest egg. But new data from TD Ameritrade indicates that older Americans are pretty behind on retirement savings, and those who don't improve risk struggling financially once their careers end.

An estimated 53% of Americans aged 50 to 59 have under $100,000 in retirement savings. And 37% have less than $50,000 socked away for the future. Meanwhile, as a good rule of thumb, it's smart to end your career with 10 times your final salary socked away in an IRA or 401(k). The average annual salary today is $51,960, according to the Bureau of Labor Statistics, which means that if you're a typical earner, you'll need roughly $520,000 to live comfortably as a senior. If you're already in your 50s with less than one-fifth that amount, consider this your wake-up call to start making changes -- immediately.

Closeup of serious older man


Ramp up your savings

Social Security provides the average senior today with about $18,000 of annual income. Clearly, that's not a whole lot to live on. If you don't have an incoming pension to look forward to (which is the case for many older workers), then you'll need savings of your own to bridge the gap between what your senior expenses look like and what your Social Security benefits pay you, keeping in mind that most seniors need roughly 70% to 80% of their former income to live comfortably on a year-to-year basis.

That's why it pays to try to sock away 10 times your ending salary for retirement. If you close out your career with $520,000, and withdraw from your savings at an annual rate of 4%, which many financial experts recommend, you'll have roughly another $21,000 a year coming your way to pay your senior living costs. But if you retire with, say, $150,000, you'll only have $6,000 of annual income to add to your Social Security payments, and that makes for a less comforting picture.

The solution? Ramp up on savings while you can. That could mean cutting back on expenses drastically to free up cash for your IRA or 401(k), getting a second job to boost your savings, extending your career, or all three.

Imagine you're 55 with $80,000 in retirement savings. If you manage to make serious lifestyle adjustments and/or boost your income with a second job so you're able to start setting aside $1,000 a month for retirement, and you continue doing so for 15 years, you'll wind up with just over $520,000 if your investment generate an average annual 7% return during that time, which is doable when you load up on stocks in your IRA or 401(k).

Even if you don't manage to get to $520,000, or thereabouts, the more you're able to save between now and retirement, the better, so make an effort to boost your savings rate even by $1,000 or so per year. The higher your nest egg going into retirement, the more long-term financial security you'll buy yourself.