Money Markets —
The plumbing of the financial system.

Money market securities are a broad class of short-term debt instruments that share one defining feature: maturity of under one year. They range from overnight to 364 days in duration. Because of their short maturity, they carry minimal price risk and are treated as near-cash instruments — which is why the 'cash' line on a balance sheet typically includes T-Bills and commercial paper, not just physical currency.

Money market securities split into two categories:

• Interest-bearing: Issued near par with an explicit coupon or interest payment. Certificates of deposit (CDs), Fed Funds, and repos fall here.
• Discount securities: Issued below par, maturing at par. The investor's return is the difference between the purchase price and face value, with no stated coupon. T-Bills and most commercial paper (CP) are discount instruments — a T-Bill purchased at 99.75 and maturing at 100 earns 0.25% over the holding period.

The money market desk at a bank trades across all of these. The role requires deep understanding of the plumbing of the short-term financial system — how banks fund themselves overnight, how the Fed controls short-term rates, and where liquidity stress first appears in the system.

The five main instruments:

• Treasury Bills (T-Bills): US government discount securities with maturities of 4, 8, 13, 26, or 52 weeks. Zero credit risk. Most liquid short-term instrument globally. Auctioned weekly. Return comes entirely from the discount to par.
• Commercial Paper (CP): Unsecured short-term corporate debt, mostly under 30 days. Issued by large, investment-grade corporations and financial institutions to fund short-term working capital needs. Slightly higher yield than T-Bills reflecting credit risk. The overall CP market is over $1 trillion in the US.
• Certificates of Deposit (CDs): Short-term deposits issued by banks, typically 30–90 days. Interest-bearing instruments issued near par. Higher yield than T-Bills, reflecting bank credit risk. Commonly offered to retail depositors as well as institutions.
• Fed Funds: Overnight unsecured loans between depository institutions, borrowing from or lending excess reserves held at the Federal Reserve. The Fed Funds rate is the primary policy rate — the Fed targets a range for this rate to implement monetary policy.
• Repos (Repurchase Agreements): Collateralised short-term borrowing — one party sells a security (usually a Treasury) with an agreement to repurchase it at a slightly higher price on a specified future date. The repo market is the largest and most operationally complex money market segment.

Money markets are generally highly liquid — often described as the most liquid segment of the debt market after Treasuries. The reasons:

• Short duration: With maturities under a year (and many under 30 days), the risk of holding any position is minimal. Buyers are willing to trade actively knowing they will get their money back shortly regardless.
• Low credit risk: T-Bills have zero default risk. Repos are collateralised. CDs and CP are issued only by high-quality institutions. Low credit risk means wide participation — more buyers means more liquidity.
• Cash-substitute function: Money market securities function as cash equivalents for corporations, money market funds, and banks. This creates constant, natural demand from institutions with short-term liquidity needs.

That said, liquidity is not uniform. T-Bills are the most liquid (vast market, zero credit risk). CP for any specific issuer can be illiquid in the secondary market — most CP is bought at issuance and held to maturity because the time to maturity is often shorter than the time needed to find a secondary buyer. Repos can seize in stress — the repo market froze temporarily in September 2008 and again in September 2019, causing sharp spikes in overnight funding costs.

Treasury Bills are US government discount securities with maturities under one year — 4, 8, 13, 26, and 52 weeks, auctioned weekly. They carry no coupon; the return is the difference between the discounted purchase price and par value at maturity.

The yield is typically very low — in normal conditions, just a few basis points above zero. Why would anyone buy them?

• They are not nothing: For a corporation sitting on $500 million in cash, earning 50bps on T-Bills rather than 0bps in a bank account generates $2.5 million per year — meaningful at scale.
• Near-zero credit risk: T-Bills are backed by the US government. In a crisis, counterparty risk on bank deposits can be a real concern (above FDIC limits). T-Bills eliminate this entirely.
• Treated as cash: T-Bills count as HQLA (high-quality liquid assets) under Basel III for banks. They appear on balance sheets as near-cash, allowing corporations and banks to maintain liquidity ratios while earning modest returns.
• Immediate liquidity: T-Bills can be sold instantly in any quantity on the secondary market. Bank deposits above FDIC limits cannot be immediately converted without notice.

In higher-rate environments (like 2023–24), T-Bill yields of 4–5% made them genuinely attractive, triggering significant corporate and money market fund flows from bank deposits into T-Bills.

Commercial paper (CP) is short-term unsecured debt issued by large, investment-grade corporations and financial institutions — typically for maturities of 1 to 90 days (rarely longer). It is issued at a discount to par, like T-Bills. The market is slightly over $1 trillion in outstanding volume in the US.

Who issues CP: Only strong investment-grade companies can access the CP market. GE Capital, Goldman Sachs, Apple, and other large investment-grade corporates and financials are typical issuers. Companies use CP to bridge short-term funding needs — think of it as a corporate credit card that gets rolled continuously. A company might issue 30-day CP today to fund working capital, then roll it (issue new CP) when it matures.

Issuance is facilitated by dealers (Goldman, JPMorgan, BAML) who build the book of investors and often backstop unsold paper — earning a placement fee of 3–6bps for their role.

Who buys CP: Primarily money market funds with mandates requiring short-duration, investment-grade assets. CP is typically bought at issuance and held to maturity — the secondary market is thin given the extreme short duration. Some corporate treasurers and banks also buy CP as a cash management tool.

Fed Funds are overnight unsecured loans between depository institutions (banks, credit unions, etc.) that hold reserves at the Federal Reserve. Banks are required to maintain a minimum level of reserves at the Fed; those with excess reserves can lend to those temporarily short of their requirement.

The Fed Funds rate is the interest rate on these overnight loans. It is the primary tool of US monetary policy — the Federal Open Market Committee (FOMC) sets a target range for the Fed Funds rate at each of its eight annual meetings. Raising the target range tightens monetary conditions (less credit, higher borrowing costs throughout the economy); cutting it loosens conditions.

The Fed Funds rate is the foundation of the US interest rate structure: essentially every other short-term rate (T-Bill yields, repo rates, bank deposit rates, the prime rate charged by banks to corporate borrowers) is priced relative to Fed Funds. Changes in the Fed Funds target ripple through the entire financial system.

Most Fed Funds lending happens overnight — banks assess their reserve position each evening and lend or borrow as needed to hit their target. The Effective Federal Funds Rate (EFFR) is the volume-weighted average of overnight transactions and is published daily by the New York Fed. The EFFR is typically within the FOMC's target range but can deviate on high-demand days like quarter-end.

Certificates of deposit (CDs) are short-term interest-bearing instruments issued by banks and large financial institutions, typically with maturities of 30 to 90 days (up to 180 days). Unlike CP — which is issued at a discount — CDs are issued at or near par with an explicit coupon.

CDs serve the same purpose for banks that CP serves for corporations: a flexible, relatively cheap source of short-term funding. Banks issue CDs when they need to raise cash quickly without going to the repo market or issuing longer-term debt.

CDs are priced relative to T-Bills of similar duration. If a 4-week T-Bill yields 4.5%, a CD from JPMorgan might yield 4.7–4.9% — the additional 20–40bps reflects the fact that CDs carry bank credit risk rather than government risk. CDs from highly-rated large banks (JPMorgan, Barclays) carry tighter spreads; CDs from smaller or lower-rated banks carry wider spreads.

Institutional buyers of CDs include money market funds, corporate treasurers, and other banks. Retail CDs (offered to individual depositors) exist on the same terms and are the form most familiar to personal finance — a bank offering a 12-month CD at 4% to individual savers is issuing the same instrument at a retail scale.

A repo (repurchase agreement) is a form of short-term collateralised borrowing. The mechanics: one party sells a security — typically a Treasury bill or note — to another party and simultaneously agrees to repurchase it at a specified future date at a slightly higher price. The difference between the sale price and repurchase price is the interest earned by the cash lender.

Example: a bank needs $100m overnight. It sells $100m of Treasuries to a money market fund today at $100m, agreeing to repurchase them tomorrow at $100,000,028 (implying approximately 1bps overnight rate). The money market fund has effectively made a secured overnight loan of $100m, earning a small return with the Treasuries as collateral.

An analogy: repo is like pawning an iPhone. You give the pawnshop your iPhone worth $500 and receive $480 cash. You agree to come back tomorrow, give them $500, and get the iPhone back. Their $20 'spread' is the overnight interest. If you don't come back, they keep the iPhone — which is worth more than they lent. They are overcollateralised and protected.

Repos are the largest segment of the money market by activity. Banks, broker-dealers, and hedge funds use the repo market constantly to fund their securities inventories and manage short-term cash positions.

A reverse repo is the opposite of a repo from the perspective of the cash provider. If Party A does a repo (borrows cash, provides collateral), Party B is doing the reverse repo (lends cash, receives collateral). Every repo transaction has a repo party and a reverse repo party — the terms describe the same transaction from different perspectives.

The Fed's reverse repo facility (RRP) became enormously important in 2021–22. The Fed offers money market funds and banks the ability to deposit cash overnight at the Fed in exchange for Treasuries, earning the RRP rate (set by the FOMC, typically 5bps below the upper bound of the Fed Funds target range).

In 2021, excess liquidity flooded the financial system (from QE and fiscal stimulus). With T-Bill yields near zero, money market funds had nowhere to earn a positive return. The Fed's RRP facility absorbed this excess — at its peak in mid-2023, the Fed's overnight RRP outstanding exceeded $2.5 trillion, as money market funds parked cash directly with the Fed rather than in the private repo market.

As rates rose and T-Bill issuance increased in 2023–24, money flowed out of the RRP back into T-Bills, reducing the Fed's RRP balance. Watching the RRP balance is a key indicator of system liquidity and short-term rate dynamics that all money market practitioners monitor.

Repos are generally safe because they are overcollateralised, but two things can go wrong:

• Collateral value collapse: If the collateral backing the repo falls sharply in value before the repo unwinds, the cash lender may hold securities worth less than the cash they lent. This happened with non-Treasury collateral (mortgage-backed securities, CDOs) during 2007–09 — the 'collateral' underpinning trillions in repo financing became worth far less than face value, and cash lenders stopped accepting it. The resulting refusal to roll repos was a critical mechanism through which the financial crisis spread through the banking system.
• Counterparty default: If the repo borrower (the party who sold the securities) cannot repurchase them at maturity, the cash lender keeps the collateral — but must now sell it in a potentially distressed market. If markets have moved against the original collateral value, a loss results.

The September 2019 repo market seizure is a more recent example: overnight repo rates spiked from ~2% to over 10% intraday as a combination of corporate tax payments, Treasury settlement, and reduced bank reserve availability caused a temporary shortage of cash in the repo market. The Fed had to intervene directly by conducting open market repo operations to inject liquidity — the first such operation in over a decade. The episode revealed vulnerabilities in how post-GFC regulations had changed bank balance sheet management around reserve requirements.

All money market instruments use the same present value / future value framework as longer-duration bonds, but with a 360-day count convention rather than the 365-day convention used for most bonds. The interest factor is:

Interest Factor = 1 + (annual rate × days/360)

For a discount instrument: the present value (price today) is:

PV = FV / (1 + annual rate × days/360)

Example: commercial paper maturing in 90 days with a 1.4% annual rate and face value of $1,000,000:

PV = 1,000,000 / (1 + 0.014 × 90/360) = 1,000,000 / 1.0035 = $996,506

The buyer pays $996,506 today and receives $1,000,000 in 90 days — earning $3,494 on a 90-day investment.

The 360-day convention (also called the money market basis) is a historical convention that simplifies calculations. Some instruments (UK Gilts, some government bonds) use 365-day conventions — always check which applies to avoid pricing errors.