What it means
For half a century, American banking had a speed limit on deposit rates. Regulation Q, created by the Banking Act of 1933, prohibited interest on demand deposits and capped what banks could pay on savings.
The Federal Reserve's history project records the origin clearly: from 1933, federal law barred interest on checking accounts and required the Fed to regulate savings rates, a regime meant to stop ruinous rate competition for deposits. The intent was stability: rate wars were blamed for weakening banks in the 1920s, so the cure was to take price competition away and let banks compete on service and toasters instead.
Price controls breed escape routes, and Reg Q's was historic: when inflation pushed market rates above the ceilings in the 1960s and 1970s, money market funds and Treasury bills offered savers what banks legally could not. The flow of deposits out of banks into funds was named disintermediation, and each episode forced the ceilings higher, proving the rule could set rates only where savers had no alternative.
Congress conceded in 1980 with the Depository Institutions Deregulation and Monetary Control Act, which phased out the ceilings over six years; the last remnant, the ban on interest-bearing business checking, survived until 2011. Reg Q's legacy is structural: the money fund industry it accidentally created is now a central nervous system of global finance, and every debate about capping bank behaviour cites its unintended children.
For a non-finance reader, Regulation Q is the cautionary tale of financial price controls: the cap held until customers found the door, and the door became an industry. The ceilings even shaped bank architecture: the grand marble branches of the mid-century were competition by other means, because a bank forbidden to outbid on price outbid on marble and location.
Internationally, the episode became a reference point in financial repression debates: capped rates work as quiet taxation of savers, and governments under fiscal pressure keep rediscovering the appeal. The final chapter closed quietly in 2011, when the last ban on business checking interest disappeared under Dodd-Frank, ending a regime that had outlived its rationale by decades.
In practice
Real-world examples.
Example
A saver moves deposits into a new money market fund yielding triple the regulated savings rate. Arithmetic beat loyalty in the end. The bank branch next door could not respond, because the ceiling capped what it was allowed to offer.
Example
A bank loses deposits every time market rates rise above its Regulation Q ceiling, a pattern named disintermediation. Its treasurer watches the Treasury bill rate against the ceiling because the gap predicts the outflow. When rates fall and the gap narrows, deposits drift back.
Example
The 1980 deregulation act phases out deposit rate ceilings over six years, ending the half-century regime. Banks begin competing on price again, and savers see higher rates on their accounts. The ban on interest-bearing business checking lingers until 2011.
Formula
Calculation
The mechanism: zero interest on demand deposits plus administered ceilings on savings and time deposits. Evasion pressure equals market rates minus the ceiling, and deposit outflows tracked that spread until deregulation in 1980-1986.
Worked example. A fictional saver holds $100,000 in a passbook account with a Regulation Q ceiling of 5.25%, earning $100,000 x 5.25% = $5,250 a year. A money market fund yielding 10.5% would pay $100,000 x 10.5% = $10,500, so the evasion pressure is 10.5% - 5.25% = 5.25 percentage points, or $5,250 a year on this balance. If just 20% of a bank's $50,000,000 of such savings moves to the fund, the outflow is 20% x $50,000,000 = $10,000,000.Case study
Seen in the real world.
This case study is fictional and illustrative. A made-up small-town bank president in Ohio watches 1979 with dread. Treasury bills yield roughly double what Regulation Q lets her pay on savings, a ceiling of 5.25%, and her passbook holders are learning arithmetic from the newspaper. Her board minutes from that year trace the slow-motion crisis: a local brokerage opens a money market fund desk two streets away, deposits leak by millions a month, and her tellers report customers withdrawing savings to buy the funds in the lobby across the street.
The bank survives on mortgage income and loyalty, but the president's annual letter to shareholders that year abandons the industry's traditional defence of the ceilings: a rule that protects banks by hiding better options from customers protects neither for long. When phase-out arrives in the early 1980s, her bank reprices deposits and wins back much of the outflow within two years. Retiring in 1988, she tells the state banking association that Reg Q's real product was not stability but the money market fund, an industry built entirely from her former customers.
Watch out
Common mistakes.
- Remembering Reg Q as ancient history; the ban on interest-bearing business checking lasted until 2011, and the regime's logic shapes rules still debated today.
- Assuming the ceilings worked as designed; they suppressed competition until alternatives existed, then amplified instability through outflows.
- Missing the unintended legacy; money market funds, now systemically central, were born as a Reg Q escape route.
Questions
People also ask.
What was Regulation Q?
The 1933-era US regime capping deposit interest rates and banning interest on demand deposits, phased out in the 1980s after money market funds exploited the ceilings.
Why did it end?
Inflation pushed market rates far above the ceilings, and savers fled to unregulated alternatives, forcing Congress to deregulate through the 1980 Act.
What did it create accidentally?
The money market fund industry and the broader shadow banking system, both born as escape routes from regulated deposit rates.
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