There are two types of Johansen test, either with trace or with eigenvalue, and the inferences might be a little bit different.4 The null hypothesis for the trace test is that the number of cointegration vectors is r = r* < k, vs. the alternative that r = k. Testing proceeds sequentially for r* = 1,2, etc. and the first non-rejection of the null is taken as an estimate of r. The null hypothesis for the "maximum eigenvalue" test is as for the trace test but the alternative is r = r* + 1 and, again, testing proceeds sequentially for r* = 1,2,etc., with the first non-rejection used as an estimator for r.
Just like a unit root test, there can be a constant term, a trend term, both, or neither in the model. For a general VAR(p) model:
There are two possible specifications for error correction: that is, two vector error correction models (VECM):
1. The longrun VECM:
2. The transitory VECM:
The two are the same. In both VECM,
Inferences are drawn on Π, and they will be the same, so is the explanatory power.
Johansen, Søren (1991). "Estimation and Hypothesis Testing of Cointegration Vectors in Gaussian Vector Autoregressive Models". Econometrica. 59 (6): 1551–1580. doi:10.2307/2938278. JSTOR 2938278. /wiki/Econometrica ↩
For the presence of I(2) variables see Ch. 9 of Johansen, Søren (1995). Likelihood-based Inference in Cointegrated Vector Autoregressive Models. Oxford University Press. ISBN 978-0-19-877450-1. 978-0-19-877450-1 ↩
Davidson, James (2000). Econometric Theory. Wiley. ISBN 0-631-21584-0. 0-631-21584-0 ↩
Hänninen, R. (2012). "The Law of One Price in United Kingdom Soft Sawnwood Imports – A Cointegration Approach". Modern Time Series Analysis in Forest Products Markets. Springer. p. 66. ISBN 978-94-011-4772-9. 978-94-011-4772-9 ↩