Are Intraday Volume and Volatility U-Shaped After Accounting for Public Information?

No matter how pronounced intraday patterns may appear, it is difficult to account for cross-correlations among related assets when those assets trade continuously and simultaneously. Futures contracts are auctioned periodically and sequentially on the Tokyo Grain Exchange (TGE). Even though intraday TGE volume is U-shaped, intraday volatility is closer to L-shaped. After accounting for the public information in immediately preceding auctions for the same commodity, for earlier trading in other commodities, and for trading on overseas markets open overnight in Tokyo, the intraday patterns are effectively flat. Thus, the timing of privately informed traders cannot be the source of intraday patterns.