The 3-6-3 rule is a historical banking joke about paying 3% on deposits, lending at 6%, and leaving work for golf at 3 p.m.
The 3-6-3 rule is a historical banking joke: pay depositors 3%, lend money at 6%, and leave for the golf course by 3 p.m. It caricatures an era when regulated deposit rates, local banking markets, and traditional loan-deposit intermediation were thought to make bank earnings simple and predictable.
It was never a law, supervisory rule, standard pricing formula, or accurate description of every bank. The three numbers are rhetoric, not evidence of a 3% profit margin.
3 is a deposit rate, 6 is a loan rate, and the last 3 is a time of day.6% - 3% = 3% is a simple rate spread, not Net Interest Margin or net profit.| Number | Intended meaning | What it omits |
|---|---|---|
| 3% | Rate paid on deposits | Deposit mix, non-interest-bearing balances, operating cost, runoff, and wholesale funding |
| 6% | Rate charged on loans | Credit losses, unused funds, loan fees, duration, prepayments, capital, and liquidity |
| 3 p.m. | Banker leaves for golf | Operations, underwriting, collections, payments, compliance, risk, and customer service |
The joke depends on the idea that a bank can lock in a stable spread with little effort. Actual bank earnings depend on balance weights, timing, risk, and expenses.
The apparent spread is:
6% loan rate - 3% deposit rate = 3 percentage points
That calculation compares two quoted rates. It does not account for how much is lent, how much funding bears interest, whether balances are average or period end, or what the bank spends and loses.
Assume Old Town Bank has this simplified average balance sheet:
| Assets | Amount | Liabilities and equity | Amount |
|---|---|---|---|
| Loans yielding 6% | $100 million | Interest-bearing deposits costing 3% | $70 million |
| Cash and premises | $10 million | Non-interest-bearing deposits | $20 million |
| Other non-interest-bearing liabilities | $15 million | ||
| Equity | $5 million | ||
| Total | $110 million | Total | $110 million |
Annual interest income is:
$100 million x 6% = $6.0 million
Annual interest expense is:
$70 million x 3% = $2.1 million
Net Interest Income is therefore:
$6.0 million - $2.1 million = $3.9 million
With $100 million of average earning assets, NIM is 3.9%, not 3%. The difference arises because only $70 million of funding incurs the stated 3% interest cost.
Now add:
Simplified pre-tax income is:
$3.9 million + $0.4 million - $1.0 million - $2.8 million = $0.5 million
The bank earns only $0.5 million before tax despite the apparent 3-percentage-point loan-deposit spread. The example ignores many additional accounting, capital, and risk effects but shows why the joke is not a profitability formula.
Beginning in the 1930s, U.S. law prohibited interest on demand deposits and authorized ceilings on rates paid on time and savings deposits. The Federal Reserve’s Regulation Q and similar restrictions for other insured institutions were intended partly to limit rate competition.
These controls fit the later 3-6-3 stereotype because banks could not freely bid deposit rates upward. But the ceilings were only one part of the environment; branching limits, local markets, product restrictions, monetary conditions, and relationship banking also shaped competition.
As market rates rose in the late 1960s and 1970s, regulated deposit rates often lagged alternatives. Depositors shifted funds toward market instruments and money market mutual funds, a process called disintermediation. Banks and thrifts could lose funding even though their quoted deposit cost remained capped.
This history is an important correction to the joke: a low regulated funding rate was not useful when customers could move money elsewhere.
The Depository Institutions Deregulation and Monetary Control Act of 1980 began phasing out deposit-rate ceilings. The Garn-St Germain Depository Institutions Act of 1982 accelerated competition through products including money market deposit accounts.
Deregulation did not end traditional spread banking. It changed the pricing environment and made funding costs more responsive to markets and customer choices.
A 6% loan yield is not attractive if defaults, charge-offs, or collection costs consume the spread. Loan pricing must reflect expected loss, unexpected loss, capital, and operating cost.
Fixed-rate assets and repricing deposits can expose earnings and economic value when rates change. A bank cannot assume that the 6% asset yield and 3% funding cost remain aligned.
Deposits can leave before loans mature. Banks need cash, collateral, borrowing capacity, and contingency plans, not merely a positive spread.
Bank Capital absorbs losses and constrains balance-sheet growth. Deposits fund assets but do not replace loss-absorbing capital.
Branches, employees, underwriting, servicing, payments, technology, security, compliance, audit, and insurance must be paid before spread revenue becomes profit.
Income taxes, assessments, consumer rules, prudential standards, reporting, and supervisory expectations affect products and returns.
Modern banks can earn Non-Interest Income from payments, servicing, fiduciary activities, trading, advice, and other services. These businesses add revenue and new risks.
| Concept | Calculation | Why it is different |
|---|---|---|
| Quoted loan-deposit spread | Loan rate minus deposit rate | Ignores balance weights and other funding |
| Cost of Funds | Interest expense / stated funding base | Requires a defined denominator and period |
| Net interest income | Interest income minus interest expense | Dollar amount before provisions and operating costs |
| Net interest margin | Annualized NII / average earning assets | Scales net interest earnings by earning assets |
| Return on assets | Net income / average total assets | Includes broader revenue, provisions, expenses, and taxes |
The 3-6-3 rule survives because it compresses a large change in banking into a memorable line. It can introduce discussions of:
Its value is explanatory and historical. It should not be cited as evidence that old banks literally followed a uniform 3%-6% pricing policy or stopped work at 3 p.m.
Use 3-6-3 rule when discussing banking history, regulation, or the limitations of simple spread models. When analyzing a real bank:
This article provides general financial education and banking history, not banking, accounting, regulatory, legal, tax, or investment advice. Historical conditions varied across institutions, jurisdictions, products, and periods.