(Bloomberg) -- The next U.S. president and Congress will face aserious test: What to do, if anything, about the nation'sretirement crisis?

Americans aren’t saving nearly enough in their 401(k)s, whilewide swaths of the workforce aren't saving at all, because theydon’t have access to a retirement plan.

Social Security, meanwhile, faces a financialshortfall as the baby boomers enter retirement.

On the Democratic side of the aisle, the election breathed newlife into an old idea that still seems outlandish to many inWashington: Why not help Americans save more for retirement byexpanding the 80-year-old Social Security program?

Related: Democratic party shifting left on SocialSecurity reform

It became a key plank in Vermont Senator Bernie Sanders’s campaign for the WhiteHouse. Hillary Clinton also proposed modestly expanding SocialSecurity, while President Barack Obama said he supported the ideaearlier this year.

Is expanding Social Security the right thing to do? Is it evenpossible?

Yes and yes, Jesse Rothstein argues. A 42-year-old professorof public policy and economics at the University of Californiaat Berkeley, Rothstein was chief economist at the U.S. Departmentof Labor earlier in the Obama administration.

His essay, “Expand Social Security,” was included among morethan a dozen policy proposals for the next president released thisweek by the Washington Center for Equitable Growth, a think tank,with ties to the Clinton campaign, that focuses on economic inequality.

Here, in an interview edited for space and clarity, Rothsteinmakes his best argument for a provocative idea.

How dire is the retirement situation for Americans?Is “crisis” the right word?

The only problem with the word “crisis” is that it didn’t happenovernight—it’s a very slow-rolling crisis. An awfully large numberof people hit retirement with nothing to live on except SocialSecurity benefits, which were never meant to be big enough tosupport you exclusively. [Franklin Roosevelt] talked about the“three-legged stool,” that Social Security would be basicallyone-third of the solution to the retirement puzzle.

Related: Retirement crisis? Do you really need toask?

Along with pensions and private savings.

Exactly. And we’ve never really gotten the other two legs of thestool strong enough, or widespread enough, to keep it level.

A lot of ideas are out there to improveretirement. You’ve got states, including now California, requiringevery worker to have access to a savings account. You have401(k)s “nudging” workers into saving by automatically signing themup. You don't seem to think those ideas are really moving theneedle. Why?

Well, some of these efforts have some impact. If you set up your"nudge" right, you can raise the share of people participating intheir 401(k) plan by a few percentage points.

But you don’t raise it to 100 percent, and there are still anawful lot of people who don’t participate. States trying to set upportable plans is a good idea, and we should be doing that. Butultimately what all these plans are relying on is voluntarycontributions from people who aren’t necessarily making enoughmoney to be able to make those contributions.

Social Security offers two things that you can’t really getthrough anything other than defined-benefit pensions, which areless and less common.

One, a Social Security payment is an annuity: The money keepscoming as long as you live. That’s really useful. If you’re livingon private retirement savings, even if you saved enough, you haveto be very careful how you spend it down, because you don’t knowhow long you need it to last.

The other thing that Social Security solves is market risk. Webasically leave it to people to figure out how to invest their ownretirement savings, sometimes with guidance from their employers,sometimes not.

They’re often taken advantage of by financial advisers who don’thave their best interests in mind and by mutual fund companies thatcharge very high fees. But even if they invest perfectly, there’sstill a risk that, as they’re getting closer to retirement, [amarket event like] 2008 happens. They thought they had enough moneyfor retirement, and then, all of a sudden, they don’t.

So what are you proposing?

We should be expanding Social Security. We should be making itmore generous.

That will require more revenues, but this is not taking moneyaway from people. It’s just giving people a better way to save forretirement.

Instead of having the Social Security payroll tax rate be 6.2percent, we could make it 7.2 percent, and all of a suddeneverybody’s Social Security benefit gets 15 percent larger.

Second, the share of income not covered by the Social Securitytax has gone way up as inequality has gone up. [Currently, workerspay Social Security taxes only on incomebelow $118,500.]

If we raise the cap and start taxing higher incomes, we canexpand benefits by a lot without increasing the burden onmiddle-class workers. We can also use that money to help cover thefinancing shortfall we have under the current system.

Third, we should create ways for people to “top up” their SocialSecurity benefit. If somebody wants to save more, then we shouldgive them a way to contribute more and get a promise of higherbenefits later.

It would be much cheaper, in terms of administrative costs, thancurrent private accounts, and it would offer benefits you can’t getthrough private accounts.

How does this fit with what Donald Trump has been talking about? He says hedoesn't want to cut Social Security, but he’s also said he won’texpand it. He is also proposing the largest tax cuts ever,$6.2 trillion over the next decade.

It’s hard to see how you could actually implement that withoutpretty dramatic cuts to Social Security.

Turning to Hillary Clinton, how does the idea ofexpanding Social Security fit in with what she’s alreadyproposed?

She’s made sensible proposals but not dramatic efforts in thisarea. Which is fine. It hasn’t been that much a part of theconversation yet. She certainly hasn’t proposed my exact plan.

Can we afford this? We already have a Social Security financing shortfall when thebaby boomers are fully retired.

I think the shortfall we have is manageable. You’d rather nothave it, but there are perfectly straightforward ways to addressit.

If the question is, “Can we afford more generous Social Securitybenefits?” the right way to think about it is, we’re asking peopleto afford lots of private retirement savings in addition to SocialSecurity.

It doesn’t make it any less affordable to move it into theSocial Security system rather than outside of it.

And, again, Social Security offers you a much more robustbenefit. The goal should be telling people not to save quite somuch in their 401(k) or their IRAs, because Social Security isdoing it for them.

Is one of the goals here to make clear to peoplethat Social Security is going to be around when they’reolder?

I guess the right way to phrase it is, if they want it to bethere, it will be there. If the American people all conclude wedon’t want it anymore, then it will go away.

But every poll I’ve seen says people really value it and don’twant it to go away. And there’s no reason why it needs to.

There’s pretty broad-based consensus that we shouldn’t becutting Social Security. We should be moving that conversationforward. We should be figuring out ways to make Social Security domore—because it can, and we need it.

You’re talking about raising taxes to pay for moregenerous benefits, which would help baby boomers and otherretirees who didn't pay this higher amount into the system to beginwith.

There are ways to structure this so you raise the taxes ahead ofwhen you pay the higher benefits. I don’t think that’s a greatidea. I don’t think we should be raising taxes now and saving themfor 30 years. But you could do that if you want to. Everygeneration of workers works very hard and deserves a secureretirement.

What about the argument that expanding SocialSecurity might discourage private saving?

To some extent the goal is to discourage private savings. We’reencouraging people to save in ways that are not very well targetedto supporting them in retirement.

Expanding Social Security is a way of telling people: You don’tneed to do that; here’s a better way.

So what happens if the next administration andCongress do nothing about retirement? What if we keep the statusquo?

The threat is that the vast majority of workers retire withoutenough to live on. People will continue to save, to try to assurethemselves a secure retirement.

Related: Boomers don't know how unprepared they arefor retirement

And some of them will get it, and some of them won’t, due tofactors entirely outside their control.

Copyright 2018 Bloomberg. All rightsreserved. This material may not be published, broadcast, rewritten,or redistributed.