Mergers and acquisitions among investment managers in 2017 reached levels not seen since the aftermath of the financial crisis, with the market under intense pressure to consolidate. While the total value of announced deals hit $40.9bn, the highest since 2009, the volume of transactions fell to its lowest since 2006, reflecting a trend of fewer but larger deals among mid-tier players, according to numbers compiled for FTfm by Dealogic, the research company.