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TESTING INTERNATIONAL PRICE TRANSMISSION UNDER ...

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Empirical Analysis: Cointegration Models, Structural Breaks and Policy Reform<br />

explained in paragraph 3.3.1, the risk is that, without considering the presence of<br />

structural breaks, prices could result I(1) processes while indeed they are<br />

stationary around a broken level or trend. Although the standard unit root tests<br />

carried out in the two sub-samples identified as before and after the MacSharry<br />

reform (reported in annex B), that find all the series I(1), are an indirect<br />

confirmation of the appropriateness of this reasoning, also specific unit root tests<br />

which allow for the presence of one or more endogenous structural breaks are<br />

carried out.<br />

The presence of unit roots allowing for structural breaks has been tested with<br />

the Perron and Vogelsang (1992), both additional outlier (AO) and innovational<br />

outlier (IO) tests, and with Clemente et al. (1998) tests (for a description, see<br />

paragraph 3.3.1). The dataset is the same as the one described in paragraph 4.4<br />

and used for the analysis in chapter 5. All prices have been used in logarithmic<br />

form. Results are reported in tables 6.1 and 6.2. In order to better understand the<br />

behaviour of the French price, the intervention price time series has been<br />

examined, as well.<br />

98<br />

Table 6.1 Perron and Vogelsang (1992) tests<br />

AO model IO model<br />

Lags Time of t stat on 5% Lags Time of t stat on 5%<br />

the break (ρ-1) critical value the break (ρ-1) critical value<br />

swfrt 12 1993:08*** -3.082 -3.560 12 1993:05*** -4.549** -4.270<br />

pintt 14 1993:08*** -1.814 -3.560 13 1993:04*** -5.810** -4.270<br />

hrwt 1 1986:05*** -3.998** -3.560 1 1985:01*** -4.191 -4.270<br />

***indicates rejection of the null hypothesis at 1%; ** at 5%; * at 10% significance<br />

swfr t<br />

pint t<br />

hrw t<br />

Table 6.2 Clemente et al. (1998) tests<br />

AO model IO model<br />

Lags Time of t stat on 5% Lags Time of t stat on 5%<br />

the break (ρ-1) critical value the break (ρ-1) critical value<br />

12<br />

1993:08***;<br />

1998:01 ***<br />

-3.719 -5.490 12<br />

1993:05***;<br />

1997:12***<br />

-5.934** -5.490<br />

14<br />

1993:08***;<br />

-2.092 -5.490 13<br />

1993:04***;<br />

-6.838** -5.490<br />

17<br />

2001:08 ***<br />

1986:09***;<br />

1996:02***<br />

-3.968 -5.490 1<br />

2001:05***<br />

1985:01***;<br />

2000:06**<br />

***indicates rejection of the null hypothesis at 1%; ** at 5%; * at 10% significance<br />

-4.562 -5.490<br />

As expected, the behaviour of the French price follows the one of the<br />

intervention price, due of course to the strong regulatory framework in place.

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