South Korea Corporate Bond BBB- 3Y Yield

KRCORPBBB is the raw-data series that records, without any transformation, the yield-to-maturity quoted daily on an unsecured three-year BBB- rated Korean won corporate bond. This yield is the single discount rate that equates the present value of the bond's promised coupon and principal cash flows to its market price, and the systematic measurement of such yields across many bonds and over time was established early on (Macaulay 1938).

KRED stores this number exactly as observed and treats the quoted yield as one point on a credit-risky term structure. This point can be read as the average of expected future short rates plus a maturity risk premium (Hicks 1939).

The same yield sits above the riskless coupon-bond term structure recovered from market prices, and that riskless curve is fitted by several standard estimators. These estimators are the zero-coupon discount-function spline and its coupon-tax refinement, the level-slope-curvature form, the second-hump extension, and the exponential-spline fit (McCulloch 1971, 1975; Nelson and Siegel 1987; Svensson 1994; Vasicek and Fong 1982). A measured three-year yield is therefore one ordinate of a curve produced by a daily construction procedure, and the comparative evaluation of competing estimators supports that construction (Gürkaynak, Sack, and Wright 2007; Bliss 1997).

The cash-flow weighting that ties this yield to the bond's effective term is the concept of duration, which was generalized across the full zero-coupon structure (Macaulay 1938; Fisher and Weil 1971). The gap between this BBB- yield and a comparable riskless benchmark rate is the bond's credit and liquidity compensation, and that benchmark can be the secured financing rate or the operating-target rate (Duffie 1996; Bindseil 2004).

KRED applies no transformation to KRCORPBBB, neither rebasing, deflating, smoothing, nor seasonal adjustment, and stores the daily quoted yield in the same units in which it is reported. The series exists because a credit-rated bond's price converts into an internal rate of return, namely the yield-to-maturity, and because a representative BBB- three-year yield is read off a fitted credit-class term structure rather than off a single bond (Macaulay 1938).

That fitting rests on the zero-coupon discount-function recovery and its tax-adjusted variant, the exponential-spline smoothing, the level-slope-curvature parameterization, and the additional curvature term (McCulloch 1971, 1975; Vasicek and Fong 1982; Nelson and Siegel 1987; Svensson 1994). The daily off-the-run construction protocol and the comparative evaluation of these estimators describe how such a curve is produced in practice (Gürkaynak, Sack, and Wright 2007; Bliss 1997).

The yield's economic content lies in its decomposition into forward rates and a risk premium (Hicks 1939). Its sensitivity to rate moves is summarized by the duration measures (Macaulay 1938; Fisher and Weil 1971).

Its excess over a riskless reference defines the credit spread above that reference, and the reference can be the collateralized rate or the operating rate set within the policy corridor (Duffie 1996; Borio 1997). KRED leaves this credit spread embedded in the raw level.

As the financing cost of a marginal investment-grade Korean borrower standing at the boundary of speculative grade, the BBB- three-year yield is a barometer of corporate credit conditions and of how monetary policy is transmitted into private borrowing costs. Its level is anchored at the short end by the monetary-policy operating-target rate, whose design and corridor mechanics, daily determination in the overnight market, and measurement transaction by transaction characterize this anchor (Bindseil 2004; Borio 1997; Bartolini, Bertola, and Prati 2002; Hamilton 1996; Furfine 1999).

Because the term-structure mapping from that policy anchor out to a three-year horizon is the expectations-plus-premium relation (Hicks 1939), movements in the BBB- yield decompose into shifts in the expected path of riskless rates and shifts in the credit and liquidity premium over the riskless curve (McCulloch 1971; Nelson and Siegel 1987).

Because the spread is measured against a riskless benchmark such as the secured financing rate (Duffie 1996), a widening BBB- yield at an unchanged policy rate signals tightening credit supply and rising default compensation. This signal is a cyclical credit-risk indicator that complements the duration-based interest-rate sensitivity (Macaulay 1938; Fisher and Weil 1971).

In valuation the BBB- three-year yield is the discount rate that prices the cash flows of comparable credits. A portfolio manager reads it as a yield-to-maturity and converts it into price sensitivity through Macaulay duration and the term-structure duration, the basis for immunizing a liability against rate moves (Macaulay 1938; Fisher and Weil 1971).

In relative-value and carry trades this yield is compared with the fitted riskless curve and the daily benchmark curve (McCulloch 1971, 1975; Nelson and Siegel 1987; Svensson 1994; Vasicek and Fong 1982; Gürkaynak, Sack, and Wright 2007; Bliss 1997). Through this comparison a trading desk isolates the residual credit spread, hedges it with riskless-rate instruments, and tracks it over time.

The forward-rate content of the curve lets desks lock future financing costs and price forward-starting exposures (Hicks 1939). The spread of the BBB- yield over a collateralized financing rate governs repo haircuts and the funding cost of carrying the position (Duffie 1996).

Because the bond sits one notch above speculative grade, even small yield moves carry outsized mark-to-market and rollover-risk consequences for leveraged holders.

On the 6,460 daily observations spanning 2000-09-30 to 2026-06-10, fit with a constant and trend, the unit-root battery agrees that the BBB-minus corporate bond yield 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 = 0.3779, the nonparametric Phillips and Perron (1988) test concurs with p = 0.6119, 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 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 = 52.22 and Q = 114.08 and p = 0.000 and p = 0.000, and the automatic portmanteau test of Escanciano and Lobato (2009) concurs with a statistic of 4.58 at p = 0.032.

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).