And that simply won't be enough to cover promised benefits. Already, administration trustees are projecting an average annual deficit of $77 billion between this year and 2018. Things will only get worse after that, as the wave of retiring baby boomers assures the number of beneficiaries will grow substantially faster than the number of workers paying into the program. 

Beneficiaries of the Disability Insurance Trust Fund are bracing for more immediate benefit reductions. By law, Social Security assets can't be used to fund that program. Trustees expect it to be fully depleted by the end of 2016. 

"Lawmakers need to act soon to avoid automatic reductions in payments to DI beneficiaries in late 2016," the trustees wrote in their most recent annual report. 

Larson's bill has been assigned to the House Ways and Means Committee, which has jurisdiction over Social Security. The chairman of that committee — influential Republican Paul Ryan – will decide whether it gets reviewed. 

While Larson's office is hopeful, at least one of the bill's proponents is doubtful Ryan will give the proposed law a full vetting.

"Since he (Ryan) has been a strong advocate of President Bush's plan to privatize Social Security, and since it's up to the chairman to decide what legislation gets taken up by his committee, he is not likely to take up the legislation," said Nancy Altman, co-director of Social Security Works, a non-profit that lobbies on behalf of Social Security's preservation.

The bill has also been sent to the House Education and Workforce Committee and the Budget Committee, according to Ed Skowronek, press secretary for Larson.

"So far it's the only bill that strengthens benefits and keeps the trust funds solvent," he said. "And it proves you don't have to cut benefits. Congressman Larson is looking forward to re-introducing it in the 114th Congress. We're optimistic that Ways and Means will take it up for consideration.'

With all of that in mind, what follows is a look at what appear to be the most important provisions of Larson's proposal, along with what the actuaries who watch over Social Security had to say about them. 

The good news is that the Social Security 2100 Act scores well, according to a letter to Larson from Stephen Goss, chief actuary at the Social Security Administration. 

The proposal scores so well, in fact, that it ultimately reduces the combined programs' reserves to 147 percent of annual costs at the end of a 75-year projection period in 2087. 

A reserve level of 150 percent is considered to be solvent, meaning Larson's bill would leave Social Security funds with a small surplus 75 years from now, according to the actuarial estimates. 

And, now, here are the four core provisions of the proposal, and how the actuaries think they will change things at Social Security.

Photo: Rep. Larson.

1. Invest up to 25 percent of trust fund reserves in equities, fully effective in 2025 

By law, Social Security income is invested on a daily basis and restricted to securities guaranteed by the federal government. These "special issue" securities are only held by Social Security trusts, and are different from "marketable" securities — those bought by institutions and investors — in that they can be redeemed before maturity without suffering a loss in principal. 

Larson's bill would set a more aggressive course, investing 25 percent of fund assets in equities by 2025, with a phase-in beginning in 2016. 

Social Security actuaries believe equity returns will be lower in the future, owing in part to lower volatility as more investment dollars move into passively managed index funds. 

They also account for the cost of investing in equities, at 0.5 basis points annually. They assume an average annual return of about 6.4 percent on equities, roughly 3.5 percentage points more than the expected yield on long-term treasuries (about 2.9 percent). 

While it sounds good, this provision would improve the long-range actuarial deficit by 0.38 percent of taxable payroll, according to the actuaries. 

In other words, not by much. "The change in the annual deficit for the 75^th projection year (2087) due to this provision is negligible (between -0.005 and 0.005 percent of payroll)," they wrote. 

2. Increase payroll tax rate to 14.4 percent, fully effective for 2037 

Congressman Larson's bill would spread the pain of a payroll tax increase out over time, increasing the rate annually for employers and employees by 0.05 percent each, beginning in 2018 each year until 2037. Ultimately it would mean 14.4 percent in FICA taxes annually from workers and their employers, compared to 12.4 percent under current law. 

This would raise the tax 50 cents per week cumulatively, according to a fact sheet from Lawson's staff. 

As a part of this proposal, funds would be rebalanced to the Disability Insurance trust, to equalize its status. 

Social Security's actuaries say the provision will ultimately reduce the annual deficit for the 75^th year by 1.99 percent of payroll. 

3. Apply payroll tax rate on earnings above $400,000, fully effective in 2015

The bill would have wealthy Americans pull more weight. Any wages above $400,000 would be subject to a payroll tax of 14.4 percent.  

Actuaries project that over time, this provision would reduce the deficit in Social Security in the 75^th year by 2.35 percent of payroll. 

4. Use the CPI-E index to calculate cost-of-living adjustments, effective for December 2015 

COLA adjustments are made to benefits using the Consumer Price Index for Urban Wage Earners and Clerical Workers (CPI-W). By using the Consumer Price Index for the Elderly (CPI-E) instead, Social Security's actuaries estimate that the COLA increase would average 0.2 percent per year. 

While estimating COLA adjustments based on the inflation of products specific to retirees' consumption habits makes sense on its face, it doesn't do anything to address the trust fund deficit. 

In fact it increases it, increasing the annual deficit in the 75^th year by 0.53 percent of payroll. Beneficiaries, of course, should appreciate that.