Spending More Than You Earn, Priced in FIRE Math

Every savings rate table this site has dissected, and the canonical original they descend from, prints its bottom row at a 0% savings rate. Spending more than you earn therefore leaves you without a row, and without a row comes no intuition for what the shortfall costs. A couple like the pair who told Ramit Sethi's podcast they spend 108% of what they make is not sitting one line below the floor. They are in unprinted territory, and it runs on inverted arithmetic: the shortfall compounds against you at borrowing rates that often run roughly two to three times long-run equity returns, and the climb back at any given savings rate takes longer than that rate's table row implies, because the hole accrued interest first.

That is the argument of this piece, worked end to end on one case. Three numbers get computed: how deep the hole actually is once interest is priced in, how much of a savings rate the first year of recovery really buys, and what rate hits a chosen exit date. By the end, "are we screwed" has a bounded answer with a schedule attached.

Every savings rate table stops at zero

The two savings rate tables this site has already dissected, like the canonical original they descend from, share a silent boundary. The lowest row anyone prints is a 0% savings rate, the point where you save nothing and work forever. Below that line the table says nothing at all. A 108% spender has no row, and with no row comes no feel for what a negative savings rate costs.

The gap matters because the sub-zero regime is not a mild extension of the printed table. Its axis changes. Above zero, the table measures years to financial independence. Below zero, the first milestone is the climb back to zero net worth, and that climb runs on the lender's rate, not the market's.

How to compute a signed savings rate

The formula survives the trip below zero without modification. Savings rate equals income minus spending, divided by income. Pick one income base and stay on it; after-tax is cleanest for couples because it is what lands in the account, and it matches the take-home convention the classic tables use.

Two conventions do the heavy lifting. Minimum debt payments are spending already done, so they count on the spending side. New borrowing is negative saving, and every dollar drawn on a card to cover a shortfall lowers the numerator directly. That is what makes the rate signed, and the sign is the diagnosis.

Example one. Income of $150,000 after tax against spending of $162,000 gives (150,000 - 162,000) / 150,000, a savings rate of negative 8%, a negative savings rate in the literal, signed sense. If you do not yet know your own gap, benchmark against BLS expenditure data to see how your spending compares with the national average, then compute the real number from your statements. Guessing is how spending more than you earn hides inside a two-income household for three years.

Why spending more than you earn compounds against you

Above zero, compounding works for you. Balances held in equities have historically averaged something near 7% real or 10% nominal, the standard planning figures, delivered unevenly and with no guarantees. Below zero, compounding changes employers. A revolving balance grows at the card's APR, contracted and billed monthly, immune to market mood. Average rates on accounts assessed interest, tracked in the Fed's G.19 release, have recently run above 21%, and the CFPB card market report for 2025 documents the revolving balances and double-digit rates households actually carry. Aggregate card balances in New York Fed data have hovered near record levels in recent quarters. The sub-zero regime is crowded, not exotic.

Set the coefficients side by side. A planning return near 10% nominal against a card APR near 21% means the compounding coefficient does not merely flip sides when you cross zero; it roughly doubles, and measured against real-return assumptions it approaches triple. Compound interest on debt is the same force FIRE writers celebrate, pointed the other way, and it carries a second edge the portfolio lacks. The market's 10% is an average with variance. The card's 21% is a contractual obligation that bills you regardless.

Three years at 108% of income, worked

Now the worked case, with assumptions on the table. Income of $150,000 after tax. The 8% overspend is $12,000 a year, carried on a card at 21% APR, with each year's shortfall borrowed at year-end and interest accruing after. Three years of that produces this:

Naive arithmetic says three years times $12,000 is a $36,000 hole. Interest says $44,089. The penalty is about $8,100, a fifth to a quarter on top of the raw shortfall, and it arrived without a single new purchase.

The other side of the asymmetry is the compounding those dollars never did. Invest the same $12,000 a year at year-end at a 10% nominal average and year three closes at $39,720. Identical cash flow, two regimes: plus $39,720 or minus $44,089, an $84,000 spread created by nothing but the sign of the savings rate.

The interest wall

Multiply the balance by the APR and you get the interest wall, the annual cost of standing still.

The interest wall is APR times balance. Any allocation below it means the hole still grows.

On $44,089 at 21%, the wall is about $9,260 a year, roughly $770 a month, just over 6% of the couple's income. That allocation buys nothing. It does not shrink the hole by one cent; it stops the hole from growing. Any allocation below the wall leaves the balance expanding, which is why a household spending more than income at card rates can throw 5% of income at the debt and still end the year deeper than it started.

The wall moves with the rate, and that makes refinancing a savings-rate multiplier. At a 24% APR the wall rises toward $10,600. Consolidate the same balance onto a mid-teens personal loan and it falls toward $6,600, instantly converting thousands of allocation from stoppage into principal. Below zero, the interest rate on the hole is a first-order variable, not a footnote.

Why recovery lags the table row

Suppose the couple stabilizes at 100% of income and commits a 20% savings rate, $30,000 a year, entirely to the hole. The table's 20% row describes a frictionless world, and friction is the entire story down here. In year one, interest consumes about $9,260, nearly a third of the whole allocation. Principal falls by roughly $20,700, an effective rate near 14%. The couple earns a 20% row and lives a low-teens one, and the gap closes only as the balance does.

The same drag stretches the calendar. Paying $2,500 a month against $44,089 at 21% clears the hole in about 21 months; call it two years. Then the real lag appears. A zero-net-worth couple at the same 20% rate has been compounding a portfolio since month one. This couple compounds nothing until month 22, so the financial independence date slips by roughly the whole recovery window. The table row was never wrong; it just starts at ground level, and this household is still in the hole.

Compute your exit date and required savings rate

This is where reassurance becomes a schedule.

Step 1. List every debt with its balance and APR. Each wall is balance times APR.

Step 2. Pick the target date for zero, N years out. The required annual payment is M = D * r / (1 - (1 + r)^-N), with D the debt and r the APR. The monthly version substitutes the monthly rate and month count.

Step 3. Divide the payment by income. That quotient is the required savings rate for the recovery phase.

Step 4. For life after zero, run the standard financial independence math. The target is 25 times annual spending under the 4% rule that the Trinity study popularized, and the savings rate whose row matches your date is the second number to solve for.

Worked numbers for the couple. A two-year zero target on $44,089 at 21% requires about $29,200 a year, a shade under 20% of income, which cross-checks the 21 months that a full 20% rate needs. After zero, a sustained 20% rate with a 5% real return puts the 25-times-spending target about 37 years out, and the sub-zero detour pushes the couple's total to just under 39. Table conventions vary by a point of assumed return, so treat any row as approximate, but the lag logic survives every convention. The SEC's compound interest calculator reproduces both legs, the hole and the portfolio, from monthly deposits.

Order of operations below zero net worth

Below zero net worth, the payoff-versus-investing question has a settled answer with one carve-out.

1. Stop the bleed first. Get spending to 100% of income or below. Every point of closed gap lowers every number above.
2. Capture the employer match, if one exists. An instant 50% to 100% return on contributed dollars beats any APR you carry, which is the standard exception to debt-first.
3. Clear debt priced above your expected return before taxable investing. Paying off a 21% balance is a guaranteed, after-tax 21% return. No portfolio offers that, and the guarantee is the whole point.
4. Order debts by APR, with a behavioral tie-breaker. The avalanche minimizes interest, and the long-running avalanche versus snowball debate exists because perceivable progress improves persistence. When two rates sit close together, taking the smaller balance first can buy the adherence that pure arithmetic cannot.
5. Automate the allocation on payday, before the month can claim it.

At zero, the household rejoins the printed table at its true rate. The unprinted rows stay behind, which is the only part of this regime worth missing.

The verdict on the 108% couple

Close the loops. The hole: about $44,000 after three years of an 8% overspend at 21% APR, against the $36,000 a spreadsheet-naive reading suggests. The recovery: a 20% savings rate lands as roughly 14% effective in year one and clears the debt in about 21 months. The exit: a rate just under 20% buys zero in two years, and the same rate held afterward reaches financial independence in the high thirties of years rather than never.

Are they screwed? The honest answer is a pair of numbers with dates attached, not a verdict. Every figure moves with its assumptions. A 24% APR raises the wall toward $10,600, and a fourth year of the same overspend ends the balance near $65,000. A consolidation loan or a closed gap moves the numbers the other way. Nothing in the sensitivity changes the direction of the fix.

Coaching and arithmetic turn out to be complements. The behavioral evidence says people persist at repayment when they can see progress, and what makes progress visible below zero is precisely the computed schedule: a wall priced, an effective rate known, a date circled. Spending more than you earn costs years, not worth. Years can be counted, and counted things can be paid off on a calendar.