Engle, Robert F.Ito, TakatoshiLin, Wen-Ling2009-12-082009-12-081988-04Engle, R.F., Ito, T. and Lin, W., (1988), "Meteor Showers or Heat Waves? Heteroskedastic Intra-Daily Volatility in the Foreign Exchange Market", Discussion Paper No. 246, Center for Economic Research, Department of Economics, University of Minnesota.https://hdl.handle.net/11299/55524This paper defines and tests a form of market efficiency called market dexterity which requires that asset prices adjust instantaneously and completely in response to new information. Examining the behavior of the yen/dollar exchange rate while each of the major markets are open it is possible to test for informational effects from one market to the next. Assuming that news has only country specific autocorrelation such as a heat wave. any intra-daily volatility spillovers (meteor showers) become evidence against market dexterity. ARCH models are employed to model heteroskedasticity across intra-daily market segments. Statistical tests lead to the rejection of the heat wave and therefore the market dexterity hypothesis. Using a volatility type of vector autoregression we examine the impact of news in one market on the time path of volatility in other markets.en-USWorking Paper