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18.3 Securities—Misrepresentations or Omissions—Materiality

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The plaintiff must prove by a preponderance of the evidence that the defendant’s misrepresentation or omission was material. 

A factual representation concerning a security is material if there is a substantial likelihood a reasonable investor would consider the fact important in deciding whether to buy or sell that security. 

An omission concerning a security is material if a reasonable investor would have regarded what was not disclosed to [him] [her] [it] as having significantly altered the total mix of information [he] [she] [it] took into account in deciding whether to buy or sell the security. 

You must decide whether something was material based on the circumstances as they existed at the time of the statement or omission. 


In Basic Inc. v. Levinson, 485 U.S. 224, 231 (1988), the Supreme Court adopted the standard for materiality developed in TSC Industries, Inc. v. Northway, Inc., 426 U.S. 438, 449 (1976), (whether a reasonable shareholder would "consider it important" or whether the fact would have "assumed actual significance") as the standard for actions under 15 U.S.C. § 78j(b). 

In discussing materiality, the Ninth Circuit has applied TSC Industries and Basic Inc. in various formulations. See, e.g., Livid Holdings Ltd. v. Salomon Smith Barney, Inc., 416 F.3d 940, 946-48 (9th Cir.2005) (applying Basic Inc. materiality test); No. 84 Emp’r-Teamster Joint Council Pension Trust Fund v. Am. W. Holding Corp., 320 F.3d 920, 934 (9th Cir.2003) (declining to adopt bright line rule for materiality that would require immediate change in stock price and instead engaging in "fact-specific inquiry" under Basic Inc.); In re Stac Electrs. Sec. Litig., 89 F.3d 1399, 1408 (9th Cir.1996) (applying test of whether there was substantial likelihood that omitted fact would have been viewed by reasonable investor as having significantly altered "total mix" of information made available); Kaplan v. Rose, 49 F.3d 1363, 1371 (9th Cir.1994) (applying test of whether omission or misrepresentation would have misled reasonable investor about nature of his or her investment); McGonigle v. Combs, 968 F.2d 810, 817 (9th Cir.1992) (applying test of whether there was substantial likelihood that, under all the circumstances, omitted fact would have assumed actual significance in deliberations of reasonable shareholder).