U.S. Effective Federal Funds Rate

USEFFR is the published effective rate on overnight unsecured lending of reserve balances, recorded as-is without any transformation, a single daily number in percent per annum that aggregates the rates struck in executed transactions, weighted by transaction volume.

The rate is therefore a market outcome measured from trades rather than a level chosen and announced. Its daily determination reflects the clearing of the market for reserves, including the reserve-maintenance structure and the liquidity effect that shape it (Hamilton 1996), and the constituent loans are identified and weighted at the level of individual transactions, which is what makes a volume-weighted summary of executed rates a measurable object at all (Furfine 1999). What is measured is a rate of interest in the sense of the price equating present and future income (Fisher 1930).

The administered settings that bracket and steer this rate are separate objects. The announced boundaries of the operating-target range are served as USFFUPPER and USFFLOWER, the rate paid on reserve balances is served as USIORB, and the steering of an overnight rate toward a target inside a standing-facility corridor by open-market operations and facilities is the subject of the operating-procedure literature (Bartolini, Bertola, and Prati 2002; Bindseil 2004; Borio 1997).

The secured overnight financing market is a distinct market whose rate falls below general levels when collateral trades special, and KRED serves that rate as USSOFR (Duffie 1996). The spreads this platform publishes between such rates are separate series in their own right, and no spread is computed here.

Through the term-structure lens the rate is the shortest maturity point and the origin from which longer yields decompose into expected future short rates plus a premium (Hicks 1939). It is quoted under the yield-to-maturity convention that ties a rate to the timing of cash flows, a timing that collapses to one day at the overnight horizon (Macaulay 1938), and from this anchor the zero-coupon curve is recovered from coupon-bond prices and expressed through parsimonious parametric forms and operational daily curve building (McCulloch 1971; Nelson and Siegel 1987; Gürkaynak, Sack, and Wright 2007). None of these constructions are applied to USEFFR itself, which remains at the recorded level.

KRED applies no transformation to USEFFR and stores the rate exactly as recorded, neither rescaling, deflating, smoothing, nor annualizing it. The methodology is therefore solely the measurement basis by which a transaction-based overnight rate comes to exist.

That basis is the identification of individual overnight unsecured loans and their aggregation into a single daily number, in which each executed transaction contributes its own rate weighted by its amount (Furfine 1999). The rate so measured is the one whose daily level reflects the clearing of the market for reserves (Hamilton 1996), each constituent rate is quoted under the simple money-market convention that maps a price into an annualized return (Macaulay 1938), and weighting interest rates by the balances they apply to is the index-theoretic operation that makes such an aggregate well defined (Diewert 1976).

Because the overnight rate is the reference of an operating target, its recorded path reflects the daily liquidity operations conducted within a corridor and the administered settings that bound it (Bartolini, Bertola, and Prati 2002; Bindseil 2004; Borio 1997).

The rate is distinct from the secured financing rate that responds to collateral scarcity, and this distinction is preserved intact in the raw series (Duffie 1996).

The same recorded overnight rate serves as the short-end input to discount-function and zero-coupon term-structure estimators that recover yields and forward rates from coupon-bond prices. Those estimators are implemented as cubic splines and their tax-adjusted refinement, as exponential splines, as parsimonious or extended parametric forms, and as the now-standard daily curve construction, they have been compared against one another, and the resulting term structure leads on to duration measurement (McCulloch 1971, 1975; Vasicek and Fong 1982; Nelson and Siegel 1987; Svensson 1994; Gürkaynak, Sack, and Wright 2007; Bliss 1997; Fisher and Weil 1971). None of that construction is applied to USEFFR itself, which remains at the recorded level.

The effective overnight rate is the outcome that monetary policy implementation aims at, the object the announced range brackets and the administered rates steer, and its daily determination reflects the supply of and demand for reserves in the overnight market, read at the level of individual transactions (Hamilton 1996; Furfine 1999).

Steering it inside a standing-facility corridor is the operational task that the theory of operating targets and the survey of operating procedures describe (Bartolini, Bertola, and Prati 2002; Bindseil 2004; Borio 1997). Where the rate settles relative to the announced boundaries is therefore read as information about reserve conditions rather than as a policy decision in itself.

The distinction between unsecured and secured overnight funding on which this rate sits is the same distinction KRED measures for Korea in the spread served as KRCALLKOFR, while the gap between an administered rate and the secured overnight rate served as KRRESV is a third object, and USEFFR is neither spread, since no spread is computed here (Duffie 1996). As a rate of interest the series is the price equating present and future income at the shortest horizon (Fisher 1930).

The current level together with its expected path moves the whole term structure through the expectations-and-premium decomposition (Hicks 1939), so its economic reach extends beyond the overnight market into the measured yield curve, whose construction runs from the yield-to-maturity convention through spline and parametric recovery to daily curve building (Macaulay 1938; McCulloch 1971; Nelson and Siegel 1987; Svensson 1994; Gürkaynak, Sack, and Wright 2007).

In valuation the effective overnight rate is the unsecured funding and floating-rate reference at the shortest horizon, so it enters the cost of carry on levered positions and the floating leg of overnight index swaps. Its formation in executed transactions and its transaction-level measurement are what make it usable as a settlement reference at all (Hamilton 1996; Furfine 1999), while the secured financing rate is the collateralized alternative against which the same cash is deployed (Duffie 1996).

The rate exposure a funding decision creates is summarized by the duration concept that maps yield to the timing of cash flows and by the term-structure duration that underlies immunization (Macaulay 1938; Fisher and Weil 1971).

Discounting and hedging require the complete zero-coupon term structure built outward from this overnight anchor, a term structure expressed through splines and their tax-adjusted refinement, exponential splines, parametric and extended parametric forms, and daily curve construction, with the methods compared one against another (McCulloch 1971, 1975; Vasicek and Fong 1982; Nelson and Siegel 1987; Svensson 1994; Gürkaynak, Sack, and Wright 2007; Bliss 1997).

Hedging and relative-value desks read the level against the announced boundaries that bracket it and against the corridor mechanics that steer it, treating the two as distinct objects since one is measured from trades and the other is chosen and published (Bartolini, Bertola, and Prati 2002; Bindseil 2004).

The effective federal funds rate summarizes the rates struck in executed overnight unsecured transactions, weighted by transaction volume, so unlike the administered limits of the target range it is a realized transaction rate. On the 6,543 daily observations spanning 2000-07-03 to 2026-07-24, fit with a constant and no trend, the unit-root battery agrees that the rate is integrated of order one. The augmented Dickey-Fuller test of Dickey and Fuller (1979), in the ARMA-consistent lag-augmented form of Said and Dickey (1984) and with lag length set as in Ng and Perron (2001), does not reject a unit root with p = 0.1793, the nonparametric Phillips and Perron (1988) test concurs with p = 0.1299, and the Kwiatkowski et al. (1992) stationarity test rejects its level-stationary null at p < 0.01, so the verdict is an unambiguous I(1). The GLS-detrended power escalation of Elliott, Rothenberg, and Stock (1996) is reserved for ambiguous outcomes under the house protocol and is not required on this clean reading.

Because the level is integrated, the mean-shift and serial-correlation diagnostics are run on the first difference, the stationary object those procedures require, since a break search or a portmanteau on an integrated level would spuriously segment and read near-unit autocorrelations (Bai and Perron 1998; Perron 1989). The multiple-break procedure of Bai and Perron (1998), computed by the dynamic-programming algorithm of Bai and Perron (2003), finds no break in the mean of the differenced series, consistent with the parameter-instability inference of Andrews (1993). The Ljung and Box (1978) portmanteau statistic, refining the original Box and Pierce (1970) form, is computed on the first difference and rejects the white-noise null at lags 10 and 20, with Q = 289.317 and Q = 311.845 and p = 0.000 in both cases, while the automatic portmanteau test of Escanciano and Lobato (2009) does not reject, with a statistic of 0.901316 at p = 0.342429. The heteroskedasticity-robust companion therefore declines to confirm the portmanteau rejections, and both readings are stated as they stand rather than reconciled.

The series is daily and has no low-integer seasonal period, so the seasonal-unit-root machinery of Hylleberg et al. (1990) and the Canova and Hansen (1995) seasonal-stationarity test are not applicable and are deliberately not run, the degeneracy of the seasonal auxiliary regression at a daily period being the standard ground (Beaulieu and Miron 1992; Ghysels and Osborn 2001).