Plains Resources' executives reported that the company found an unusually large natural gas field. As a result, the company's stock was bid up from $7.63 to $29 a share in a few months. Insiders were told that initial estimates were too high. They sold more than 30,000 shares of stock. Information about the lower estimates was then released, driving the price down to about $15. Shareholders sued, claiming that the executives traded on insider information and misled investors by not revealing bad information about the gas find more quickly. Was that securities fraud? [Rubinstein v. Collins, 20 F.3d 160, 5th Cir. (1994)]