South Korea Policy Base Rate

KRBASE is the published policy base rate, carried into KRED and recorded as-is without transformation, filtering, or interpolation. It is the administered operating-target rate that the monetary authority announces at scheduled policy meetings and holds constant until the next decision.

The base rate is the controlled level around which the overnight interbank rate is steered, the operating target, and it sits at the very short end of the term structure as the anchor from which longer yields are built up. The mechanics of such an operating-target regime are set out consistently across countries (Bindseil 2004; Borio 1997).

This target rate pins the day-to-day overnight rate within a standing-facility corridor (Bartolini, Bertola, and Prati 2002). The unsecured overnight rate that the policy rate governs is formed and measured daily at the level of individual transactions (Hamilton 1996; Furfine 1999). The unsecured overnight market that the base rate targets differs from the secured financing market, and this distinction clarifies what the base rate is and is not (Duffie 1996).

Through the term-structure lens, the base rate is the current short rate whose expected path plus a premium determines longer yields (Hicks 1939). The yields so determined are computed within a subsequent measurement tradition (Macaulay 1938; McCulloch 1971; Nelson and Siegel 1987; Gürkaynak, Sack, and Wright 2007).

The series is recorded as a daily step function, changing only on decision dates and otherwise flat.

KRED applies no transformation to KRBASE and performs neither rescaling, deflating, smoothing, nor annualizing. The methodology is therefore confined to the measurement basis by which an administered policy rate comes to exist.

The rate is not a market-clearing price but a level chosen by a policy committee and published as a percentage per annum, which constitutes an operating-target construction (Borio 1997; Bindseil 2004).

The rate is maintained within a corridor through open-market operations and standing facilities (Bartolini, Bertola, and Prati 2002). The daily microstructure of the overnight rate is measured at the level of individual transactions (Hamilton 1996; Furfine 1999).

The unsecured overnight rate that the policy rate targets is distinct from the secured repo rate, and this distinction is preserved intact in the raw series (Duffie 1996).

To situate this short rate within the measured yield curve, the same series feeds the zero-coupon and forward-rate construction. Those curve-construction methods begin with bootstrapping and continue through parametric fitting, exponential splines, their extended form, operational daily curve building, and comparative evaluation (Macaulay 1938; McCulloch 1971, 1975; Nelson and Siegel 1987; Vasicek and Fong 1982; Svensson 1994; Gürkaynak, Sack, and Wright 2007; Bliss 1997). A duration mapping then relates that level to cash-flow timing (Fisher and Weil 1971). None of these adjustments are applied to KRBASE itself, which remains at the recorded level.

The base rate is the lever of monetary policy through which the monetary authority transmits its stance into the wider economy. The operating-target framework that assigns it this role is formalized within the standard apparatus of monetary policy implementation (Bindseil 2004; Borio 1997).

Steering the rate within a corridor controls the overnight cost of reserves (Bartolini, Bertola, and Prati 2002). Reserve supply and the policy rate jointly determine the daily overnight rate, and this liquidity effect is traced and measured at the transaction level (Hamilton 1996; Furfine 1999).

The current base rate and its expected path move the entire term structure (Hicks 1939). The economic reach of the policy rate therefore extends beyond the overnight market to the whole of the measured yield curve (Macaulay 1938; Nelson and Siegel 1987; Svensson 1994; Gürkaynak, Sack, and Wright 2007).

The contrast with the secured financing rate separates the policy signal from collateral-market frictions, and this sharpens the interpretation of the base rate as a gauge of the monetary policy stance (Duffie 1996).

Because the base rate anchors the short end of every discount curve, it enters bond pricing and interest-rate risk management directly. The channel runs through the duration concept that maps yield to the timing of cash flows (Macaulay 1938) and the term-structure duration that underlies immunization (Fisher and Weil 1971).

The zero-coupon and forward curves used to discount and hedge are built from this short rate (McCulloch 1971; Nelson and Siegel 1987; Vasicek and Fong 1982; Svensson 1994; Gürkaynak, Sack, and Wright 2007).

On the funding side, the policy rate sets the floor for overnight money. Its daily formation and its steering within a corridor are well documented (Hamilton 1996; Furfine 1999; Bartolini, Bertola, and Prati 2002). The secured repo rate provides the collateralized counterpart against which floating-rate instruments and swaps are referenced (Duffie 1996).

Treasury and asset-liability desks therefore treat KRBASE as the base from which carry, rollover cost, and discount factors are computed.

On the 9,055 daily observations spanning 2001-08-23 to 2026-06-08, fit with a constant and trend, the unit-root battery agrees that the base 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 = 0.8708, the nonparametric Phillips and Perron (1988) test concurs with p = 0.9156, and the Kwiatkowski et al. (1992) stationarity test rejects its trend-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 I(1) 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 rate, consistent with the parameter-instability inference of Andrews (1993). The base rate is held constant between monetary-policy decisions, so its first difference is a sparse jump sequence close to white noise, and the Ljung and Box (1978) portmanteau, refining the original Box and Pierce (1970) form, fails to reject the white-noise null on that difference with p = 1.000 at lag 10 and Q = 18.39 at lag 20 (p = 0.561), while the automatic portmanteau test of Escanciano and Lobato (2009) concurs with a statistic of 0.34 at p = 0.559.

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 inapplicable 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).