Sorry that my previous email was done in such a hurry. I think that you have understood me perfectly. GRETL was already consistent with what I said.

John C Frain

Economics Department

Trinity College Dublin

On 26/07/06, **Allin Cottrell** <cottrell@wfu.edu> wrote:

On Wed, 26 Jul 2006, John C Frain wrote:

> Can I make a brief comment on this debate. A residual based

> test for cointegration is base on the residuals from a

> cointegrating regression. Depending on whether the variables

> in the cointegrating regression have non zero drifts on should

> include a constants or a trend in the cointegration. If this

> is done properly there is no need to include a constant or a

> trend in the cointegrating regression.

I take it you mean "in the final DF test regression" at the end

there?

What we do currently is consistent with your comment, as I

understand it. Based on the selection of case "nc", "c", "ct"

or "ctt" we include or omit the constant, trend and

trend-squared in the cointegrating regression. When we do

the DF test on the residuals from this regression, we do not

include any deterministic terms, but we select the "tau

statistic case" (that is, the distribution to which the "t"

ratio should be referred) based on the setup of the

cointegrating regression.

> Can I recommend the account in Hayashi , F (2000),

> Econometrics, Princeton University Press.

Thanks for the reference.

Allin.

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John C Frain