Any woman who isn't investing money in a 401(k) plan – or maybe only sets aside a tiny amount – needs to realize that the retirement game is stacked against her.

"Women are more at risk in their older years for economic insecurity," said Amy Matsui, director of income security and senior counsel for the National Women’s Law Center in Washington, D.C.

Here are some thoughts to motivate everyone from their 20s to 60s to stick to New Year's resolutions and save far more aggressively in 2019:

There's a gender gap in retirement

The wage gap that women experience in their working years morphs into a gender retirement gap.

"Unfortunately, women have less income rather than more when it comes to retirement," Matsui said.

Based on today's wage gap, a woman who worked full time, year round would typically lose $406,760 over a 40-year career, according to a report by the National Women's Law Center. The example assumes a constant wage gap of $10,169 each year.

To make up that lost money, a woman who fits this example would have to work nearly 10 years longer than her male counterpart.

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Taking home less money, of course, means a woman has less discretionary income to set aside toward savings. A smaller nest egg ultimately would threaten economic security later in life.

Women in nearly every occupation face a wage gap, according to Matsui. Women in the United States, who work full time, year round are typically paid only 80 cents for every dollar paid to their male counterparts, according to the National Women's Law Center.

Starting out at a lower wage often is hard to overcome, especially when raises or pay in a new job ends up being based on previous salary histories.

Matsui noted that women find it harder to save for retirement several reasons. They tend to earn less than men. They're more likely to be low-wage workers. They're more likely to leave paid work to be caregivers. They're more economically affected by divorce.

And they're more likely to work part time or for small employers, and may not be able to participate in a 401(k) plan as a result.

Some experts note that some women may be held back because they aren't comfortable demanding a raise; others may be unwilling to apply for promotions for jobs that would conflict with raising children.

Long lifespans mean bigger bills

After a couple reaches age 64, two-thirds of the women will outlive their husbands by almost 12 years, according to a 2016 study by TIAA.

The expenses associated with living alone are dramatically higher than when two people are able to share household chores and expenses. Matsui noted that women also may be more reliant on their spouse's retirement benefits.

Women age 63 on average end up with only two-thirds of the retirement savings and benefits that men do.

Women face higher health care expenses

Women age 63 and up are projected to spend 30 percent more on health care in retirement than men, according to a study by HealthView Services.

Women may be more likely to suffer through chronic illnesses and may be less likely to benefit from a spouse who serves as a caretaker.

Men and women have different life journeys

Women often can face a wealth gap, in part, because of family or life expectations set for women – ranging from parenting to care-giving duties for elders.

Two-thirds of care provided to older adults is done by women, whether involving a parent, grandparent, parent-in-law or other family member or friend, according to a Merrill Lynch-Age Wave study.

Leaving a job or cutting back on hours to take care of young children or older adults can lead to lost benefits and promotions, in addition to extra out-of-pocket costs. The average caregiver spends $7,000 a year on their care recipient.

Mothers also experience a "mommy penalty," a pay gap that is three times that of non-mothers because of lost income and missed opportunities for promotions caused by breaks from the workforce, the Merrill Lynch-Age Wage study noted.

As for good news, more women are going to college and may have access to better paying jobs than their mothers or grandmothers.

Women now graduate from college and graduate school in higher numbers than men, according to the study, which boosts their career options.

About 42 percent of women ages 18 to 64 have a bachelor's degree or higher. That's up from 25 percent in 1992.

However, women are juggling more student loan debt and then are likely to face the gender pay gap.

Women now hold about 65 percent of all student debt, according to the Merrill Lynch study conducted in partnership with Age Wave.

"It's harder for women to save and subsequently invest if they are simultaneously paying down debt and accumulating less income," the "Women & Financial Wellness: Beyond the Bottom Line" study conducted in partnership with Age Wave noted.

Such statistics, of course, are depressing to read but they're realistic in many cases, according to Melissa Spickler, managing director for the Merrill Lynch office in Bloomfield Hills, Michigan.

Millennials need to pay attention early on, she said, and begin saving for retirement as soon as they begin working. If one doesn't have a 401(k) plan at work, it's possible to set aside money elsewhere using other retirement savings vehicles, such as a Roth IRA.

Many times, Spickler said, women may not want to save for retirement when they're newly married because they think they have many years ahead to worry about retirement.

Or the husband may argue that the couple can use the woman's salary to pay the bills, while the husband dedicates more pay toward retirement savings.

But she recommends that women start saving for retirement as soon as they get that first job and keep doing so throughout their lives.

Spickler said some women may be less willing to seek outside financial advice, which they need, and instead depend too much on a husband to take care of all financial matters.

Women tend to be more risk averse when it comes to how they're investing their 401(k) savings, as well, according to the TIAA report called "Income Insights: Gender Retirement Gap."

Many times, women will have more money parked in cash instead of invested in mutual funds than men do, which can hold back how much money they'd ultimately have in retirement.

Even young workers who may be paid the same amount of money at the same company won't necessarily be equally well off in retirement.

In order for two recent college graduates to have the same amount of money saved for retirement, the young man would need to save 10 percent of his salary, while the woman would need to save 18 percent, according to the TIAA study.

Shelly-Ann Eweka, a director of financial planning for TIAA in Denver, said many young women at the start of their careers might not take into account that one day they might stop working to care for children or an elderly parent.

Some women, she said, also won't see the raises or promotions that their male counterparts would receive.

"They may not realize that going forward in the future that they'll work less and they'll get paid less," Eweka said.

To deal with those challenges, women need to save more money upfront for retirement, she said. And they need to diversify their investments, including stocks and annuities into the mix, in order to build healthier retirement balances. TIAA has a site called Woman2Woman at www.tiaa.org that lists tips.

Women won't have an easy time playing catch-up.

Often, experts say, it's hard to find a good-paying job in one's field of expertise after leaving the workforce to be a stay-at-home mom or serve as a caregiver for another family member.

"We are always the ones that stop our work," Spickler said. "Everyone else always keeps on working."

Contact Susan Tompor: stompor@freepress.com or 313-222-8876. Follow Susan on Twitter @Tompor.