If lawmakers don't act, Social Security's trust fund will be tapped out in about 18 years.

That's one takeaway from the Social Security and Medicare trustees' annual report released Wednesday.

That doesn't mean retirees will get nothing by 2034. It means that at that point the program will only have enough revenue coming in to pay 79% of promised benefits.

So if you're expecting to get $2,000 a month, the program will only be able to pay $1,580.

Technically, Social Security is funded by two trust funds -- one for retiree benefits and one for disability benefits.

The 2034 date is the exhaustion date for both funds when combined. But if considered separately, the old-age fund will be exhausted by 2035, after which it would be able to pay just 77% of benefits. And the disability fund will be tapped out by 2023, at which point it could only pay out 89% of promised benefits.

To make all of Social Security solvent for the next 75 years would require the equivalent of any of the following: immediately raising the Social Security payroll tax rate to 14.98% from 12.4% on the first $118,500 of wages; cutting benefits by 16%; or some combination of the two.

Medicare faces insolvency two years earlier than expected

In terms of Medicare, the trustees project that the trust fund for Part A, which covers hospital costs for seniors, will run dry by 2028. That's two years earlier than they projected last year, due to lower than expected payroll taxes and a slower-than-estimated rate of reduction in inpatient use of hospital services.

But the exhaustion date is still 11 years later than had been projected before Congress passed the Affordable Care Act, now known as Obamacare.

By 2028, Medicare Part A would only be able to pay out 87% of expected benefits -- a figure that would fall to 79% by 2043 before gradually increasing to 86% by 2090.

Medicare Part B, meanwhile, which helps seniors pay for doctor's bills and outpatient expenses, is funded by a combination of premium payments and money from general federal revenue. The same is true of Part D, which offers prescription drug coverage. Both will be financed in full indefinitely, but only because the law requires automatic financing of it.

But their costs are growing quickly. The trustees estimate that the costs will grow to 3.5% of GDP by 2037 then to 3.8% by 2090, up from 2.1% last year.

"Social Security and Medicare remain secure in the medium-term," said Treasury Secretary Jacob Lew. "But reform will be needed, and Congress should not wait until the eleventh hour to address the fiscal challenges given that they represent the cornerstone of economic security for seniors in our country."

Where do the presidential candidates stand?

The country's long-term debt is very much driven by entitlement program spending, particularly in Medicare. That's largely because the costs for both programs are expected to grow faster than the economy for the next two decades and then stay at or near relatively high levels for years after.

So what exactly would the presumed presidential nominees do about that?

As much as he publicly laments the country's debt, Donald Trump offers nothing in the way of substantive policy proposals to reform either Medicare or Social Security, beyond promising that he will not curb spending on them.

Instead, Trump has said he wants to recapture money from other areas of the economy to shore-up Social Security.

Meanwhile, Hillary Clinton has specified what she won't do -- e.g., raising the retirement age or cutting middle class benefits -- but she doesn't offer detailed or diverse policy prescriptions of what she would do.

For instance, she has said she wants to shore up Social Security, but then says she wants to expand benefits, which increase the program's costs.

Her only specific solution is to ask "the highest-income Americans to pay more, including options to tax some of their income above the current Social Security cap, and taxing some of their income not currently taken into account by the Social Security system."

Related: Moody's: Trump's plan would cost 3.5 million jobs

Advocates for curing Social Security's impending shortfall have pushed for changes sooner rather than later, because the longer the country waits the more abrupt and drastic the changes need to be.

They also often call for a mix of tax increases and spending cuts to reduce how steep either have to be.

As for expanding Social Security benefits, some propose making them more generous but just for the most vulnerable populations -- such as seniors living at or near the poverty line.

On Medicare, Clinton has said she would build on cost-savings initiatives created by Obamacare and allow Medicare to "negotiate for lower prices with drug and biologic manufacturers; demanding higher rebates."

Trump has said he would repeal Obamacare, but he also supports letting Medicare negotiate for better drug prices.

That alone, however, would not save the program much money unless the Health and Human Services Secretary is given authority to legally require lower prices, according to the Committee for a Responsible Federal Budget.