According to the article linked below, Fidelity and Schwab allowed the preferential, post-trade allocations to occur over a period of years. "Investigators from the SEC’s market abuse unit detected Breton's fraud through data analysis, according to the regulator. For years, Breton used “master” or “block-trading” accounts — which enable advisers to make purchases on behalf of groups of investors — to buy shares on the days companies reported earnings, according to prosecutors. Breton waited until after the companies released their quarterly results to assign the trades to portfolios he managed, investigators said." http://www.financial-planning.com/n...y-to-cherry-picking-investments-in-13m-scheme