Repo

A repurchase agreement is a loan dressed as two trades: you sell a security today and commit to buy it back tomorrow (or next week) at a slightly higher price. The price difference is interest — the repo rate — and the security is the lender's collateral throughout.

Repo is how the bond world breathes. Dealers finance their inventories with it; hedge funds lever positions through it; money funds lend cash into it; central banks implement policy with it. Daily volumes run in the trillions of dollars — it is arguably the most systemically important market almost nobody outside finance has heard of.

Because the loan is over-collateralised (you lend 98 against a bond worth 100 — the gap is the haircut) and usually overnight, repo is about as safe as lending gets. Which is precisely why, when repo does seize up, everything else does too.

Mechanics and jargon

• Repo / reverse repo: same trade from the two sides — cash borrower vs. cash lender.
• GC (general collateral): any acceptable government bond will do; the GC rate is effectively a secured policy-rate satellite (SOFR is computed from US repo).
• Specials: when everyone needs one particular bond (to deliver into shorts or futures), its repo rate falls below GC — owners of that bond can borrow cash abnormally cheaply. Specialness = a lending fee on a hot security.
• Term, open, tri-party: durations beyond overnight; tri-party agents (BNY) handle collateral operationally.

Haircuts and leverage

A 2% haircut means 50x potential leverage on government bonds — the fuel of basis trades. Haircut spirals (collateral falls → haircuts rise → forced sales → collateral falls) are the modern bank-run mechanism: Bear Stearns and Lehman died in the repo market before they died anywhere else.

Policy plumbing

Central banks steer short rates through repo: the Fed's RRP facility (floor) and Standing Repo Facility (ceiling) corral the corridor; September 2019's repo spike (rates briefly 10%) forced the Fed back into daily operations — a masterclass in why reserves scarcity matters.

Pricing relationships

Repo is the financing leg inside nearly every fixed-income arbitrage:

Specialness enters as a dividend-like yield: a special bond's forward is higher (cheaper to hold via repo), and futures cheapest-to-deliver analysis, bond rich/cheap and swap spreads all run on repo assumptions. The implied repo rate backed out of futures vs. cash is the basis trader's core number.

Specialness economics

Auction cycles, short bases, and collateral scarcity set specialness; the fails penalty (Treasury: ~3% floor) caps how special a bond can trade. Persistent specialness feeds into on-the-run premia — a liquidity/collateral value embedded in benchmark bond prices.

Systemic mechanics

• Rehypothecation chains: the same collateral secures multiple loans in sequence — efficiency and fragility simultaneously; collateral velocity is a monitored aggregate.
• Cleared vs. bilateral: post-2008 reforms push repo into CCPs (US Treasury clearing mandate phasing in) — netting shrinks balance sheets but concentrates the CCP.
• NBFI leverage: hedge-fund Treasury basis books financed at minimal haircuts are the current policy obsession (2020's dash-for-cash unwound exactly this).