The average man's retirement account contains $139,000. For women, it's $82,000.

Think of all that's happened since the start of the new year — the Oscars, March Madness, failed resolutions. Now imagine if throughout that time, all the men in the US had taken vacation while all the women worked — but the women didn't get paid any more than the men.

That's the concept behind Equal Pay Day, which this year is happening today. Women's equality advocates use Equal Pay Day to symbolize how wide the national gender wage gap is. Last year, the median full-time year-round working US woman earned 78 percent of what a comparable man earned. At that rate of pay, she'd have had to work until today to make up for that gap.

However, the wage gap isn't just about the 22 fewer cents women earn for every man's dollar. When it comes to investing for retirement, the financial difference between being a man and a woman spirals into the hundreds of thousands of dollars.

The massive retirement gap

Let's consider a man and a woman getting started saving for retirement. Let's assume they start saving at age 25. The median 25- to 34-year-old man earns $40,000, according to the Education Department, compared with $35,000 for a woman. A Bankrate retirement calculator shows that given those early salaries, the savings difference at retirement is nearly $200,000.

A lot of assumptions go into the calculations here — I gave them both 3 percent raises each year (just above inflation), and also had them contribute 10 percent every year, with modest employer matching. Also, it assumes both the man and woman work without stopping (for, say, having children) and get the same percentage-level raises.

You can tweak these assumptions for yourself on Bankrate's calculator and test out people of different education levels — the gap grows to nearly $300,000 with college graduates, for example — but the point here isn't an exact measure so much as magnitude, and that magnitude is huge.

Real-world differences

I've done the hypothetical math above, but in the real world, American men and women also have some huge retirement savings differences. The average IRA balance for men in 2012 was nearly $140,000, compared with less than $82,000 for women, according to the Employee Benefit Research Institute.

Add on top of that the fact that US women live nearly five years longer than men, and the retirement gap seems all the more yawning. Women simply need to plan for longer retirements, on average, but we systemically pay them less throughout their working lives.

Consider the guy or lady who sits next to you at the office. A minor differential in your pay right now could make a world of difference between how the two of you fare in retirement.

Paying more throughout life

Retirement isn't the only place this wage gap plays out. Even one year out of college, that woman is earning substantially less than the man — 82 percent of what he earns, according to one 2012 study from the American Association of University Women. Using Education Department wage data and assuming the man and woman both go to public four-year colleges and end up with an average debt load (just under $27,000), the young man will end up paying around $1,000 less than the woman in interest and spend nearly two years less than she does paying off loans.

A woman's lower pay doesn't just mean she can afford a lower-rent apartment or have less disposable income now. It gives her a lot less freedom to make that money work for her. Consider what that young college-grad man could do with that extra $400 each month once he finishes paying off his loans. He could buy a house earlier (likely a bigger one than the woman will be able to afford, by the way) or sock it away for retirement, making that already wide retirement gulf even wider.

And of course, lots of Americans don't even have college degrees or 401(k)s, but they're just two examples of the bigger problems the wage gap creates. Whether it's those things, buying a house, or saving up for kids' college, women simply have far fewer resources for longer-run investments. Add in the premium women pay for basic hygiene and all the unpaid work they do, and equal pay doesn't seem like such a huge thing to ask for.

Explanatory journalism is a public good

At Vox, we believe that everyone deserves access to information that helps them understand and shape the world they live in. That's why we keep our work free. Support our mission and help keep Vox free for all by making a financial contribution to Vox today.

One-Time Monthly Annual

$95/year

$120/year

$250/year

$350/year

Other

$

Yes, I'll give $120/year

Yes, I'll give $120/year

We accept credit card, Apple Pay, and Google Pay. You can also contribute via