Aon Corp. ( AON) Company Profile: Aon is a provider of risk-management services, insurance and reinsurance brokerage and human capital and management consulting. In July 2010, the company announced a merger with Hewitt Associates, an HR consulting and outsourcing company. Share Price: $46.30 (Dec. 6) 2011 Return: 0.7% Investment Thesis: William Blair analysts see several catalysts for Aon Corp. in 2012, the most notable of which is the merger with Hewitt, which should reap rewards next year. The analysts forecast a 100-basis-point improvement in pretax margin for 2012 and a 250-basis-point improvement for 2013. "The margin in the brokerage segment has finally begun showing progress," the analysts write. "With forecast organic growth remaining solid (our estimate is 3% for 2012), the segment should be able to secure additional margin expansion for the next few years. We forecast 40 basis points of pretax margin improvement during 2012 and 2013." Additionally, William Blair expects Aon's free cash flow growth to remain robust and their forecast assumes 30 million of share repurchases over the next two years, which they argue could be a conservative number if the cash flow from the merger with Hewitt. accelerates into 2012.