Headline Results & the Equity Cliff

A structured parameter study on the corrected engine, read from the live model in August 2026.

The short version

In the July 2026 model, the same payroll-tax dollars invested rather than paid into Social Security produced a dramatically better outcome — but only when invested in equities.

Under a realistic target-date glidepath, the defined-contribution (DC) alternative returned 3.7× to 8.0× the present value of Social Security across the entire income distribution, and beat it in 1,000 out of 1,000 simulated market histories. Under an all-fixed-income posture, Social Security won — decisively, at nearly every income level.

That conditionality is the finding. It is not a caveat attached to the result; it is the result.

The headline grid

Deterministic present-value ratio (DC ÷ SS). Income is the worker's peak career earnings in today's dollars. Above 1.0 means the DC path won in the model; bold means Social Security won.

Nine of the thirty cells went to Social Security — every Treasuries cell, and every Bonds cell except the taxable maximum.

The glidepath is the study's realistic base case: Equities-Aggressive to age 35, Equities-Moderate to 50, Equities-Conservative to 67, then Bonds through retirement — the standard target-date shape. The Equities-Aggressive row is a single sector fund compounding for 77 years, reported only as a bounding case; no conclusion rests on it.

The equity cliff

The gap between Bonds (0.79×) and Equities-Conservative (4.71×) at the median earner is a factor of six. There is no gentle gradient between them.

In the July 2026 model, the decision that determined whether a DC system beat Social Security was not how much you earn, or when you retire, or how long you live. It was whether the money touched equities at all.

The Monte Carlo view

Trials out of 1,000 in which the DC path beat Social Security:

On the resampled-history measure the cliff was not merely sharp — it was binary. Every equity and glidepath run won every trial; every fixed-income run lost the large majority.

Income percentiles. The Monte Carlo tab now reports portfolio-income percentiles natively — directly simulating withdrawal amounts at each percentile rather than scaling them from the balance distribution. This supersedes the earlier scaling-derived estimates and gives a direct read on the range of likely retirement incomes under each strategy.

One cell deserves a warning. Bonds at the taxable maximum was the only fixed-income cell that won deterministically (1.16×) — but it won just 63 of 1,000 Monte Carlo trials. A favorable historical bond sequence carried that cell; the underlying distribution did not support it. We do not count it as a DC win. It is the clearest illustration in the study of why a single historical path should never be read alone — and where a deterministic figure and a Monte Carlo figure disagree, the Monte Carlo figure is the one to believe.

How to read this honestly

• The fixed-income result is not a footnote. A bond portfolio forced to pay Social Security's own income stream went bankrupt before the end of a long retirement at every income level in the model. A DC system without an equity mandate was worse than the system it would replace. (See the withdrawal-rule analysis.)
• Social Security's strengths are real and visible in this data. It is guaranteed, inflation-adjusted, immune to market timing and sequence-of-returns risk, and it pays for as long as you live. The DC alternative offered a higher expected outcome by transferring risk onto the beneficiary. That trade is the honest core of the comparison.
• This is a scenario study, not a population forecast. Every claim is of the form "for a median earner on a glidepath…", never "for X% of Americans." The population-weighted page handles the translation to workers — carefully, and by investment behavior.

About these figures — please read. Every number here is an output of the Is Social Security Worth It? simulator, read from the August 2026 build. These are model estimates, not predictions, advice, or guarantees; they describe how the model behaved on that date, not a promise about future versions. A July 2026 audit corrected four defects and withdrew several earlier findings (see Corrections & Retractions); figures may change in later builds. Past performance does not guarantee future results. Your actual benefit is set by the SSA at ssa.gov/myaccount. Per-cell data: DCvsSSv3core.csv, DCvsSSv3montecarlo.csv.