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Eric Hillebrand Gunther Schnabl Discussion
Paper No.6 October 2003
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ãEffects of the Bank of Japanâs intervention on yen/dollar exchange rate volatilityã21 November 2004
Toshiaki Watanabe (a), Kimie Harada(b)
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The Effects of Japanese Foreign Exchange Intervention: GARCH Estimation and Change Point Detection
Eric Hillebrand Department of Economics, Louisiana State University
Gunther Schnabl Department of Economics and Business Administration, Tuebingen
4.1. Specification
 Table 2 summarizes the stylized facts of Japanese and US foreign exchange intervention and gives the necessary information for the GARCH model specification.
First, we observe that in contrast to the US, Japanese foreign exchange intervention is highly focused on the yen/dollar market. Since 97.48% of Japanese foreign exchange intervention is against the US dollar, we exclude other yen exchange ratesâfor instance against the euro (German mark before 1999)âfrom the investigation.
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 Second, Japan has a much higher propensity to intervene in foreign exchange markets than the US both in terms of intervention days and absolute intervention volume.
The number of intervention days in the yen/dollar market is almost tenfold (Japan 215, US 22) and the discrepancy between the transactions volumes is even more pronounced (300.98 billion dollars in Japan and 8.4 billion dollars in the US).
We further observe that all 22 US intervention days in the yen/dollar markets coincide with Japanese intervention days,working parallel.
This implies that US intervention is triggered by Japanese intervention and we are faced with multicollinearity.
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To deal with both the asymmetric scope of intervention and multicollinearity, we add US and Japanese foreign exchange intervention to create one exogenous variable Iâwhich represents Japanâs efforts to redirect the yen/dollar rate.
This specification is justified by the fact that US intervention is only in support of Japanese intervention and prior tests with solely Japanese intervention as the exogenous variable did not yield significantly different results (as US intervention is negligible).
Sarno and Taylor (2002: 846) argue that coordinated sterilized intervention between two or more countries might convince speculators that the signalled policy is more credible as opposed to a single-country intervention. Yet a dummy for coordinated intervention has remained insignificant for the US-Japanese case since 1991.
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Third, dollar purchases in Japan clearly dominate intervention activities (Figure 1).
Out of 215 intervention days dollars were purchased on 182 intervention days (84.65%), on 33 days (15.34%) dollars were sold.
In terms of absolute intervention volumes (in dollars) 263.63 billion dollars were purchased (87.50%) and 37.62 billion dollars were sold (12.50%).
Due to the comparatively small amount of Japanese dollar sales we do not estimate the effects of dollar purchases and dollar sales separately, but treat intervention as one time series with positive (dollar purchases) and negative signs (dollar sales).

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