By Robert Long and Andrew Sumner ( December 18, 2018, 2:12 PM EST) -- Class actions challenging proposed corporate mergers, while down from their peak numbers in the early 2010s, continue to be filed at record levels in the federal court system. This shift from state to federal courts is now a well-documented phenomenon. In 2017, 73 percent of deals valued over $100 million were challenged by shareholders, down from 94 percent in 2013,[1] but 87 percent of those lawsuits were filed in the federal courts, compared to only 32 percent in 2013.[2] Nearly half of all federal securities class actions are now mergers and acquisitions cases.[3] Although the numbers for 2018 have not yet been finalized, there are no signs this trend has eased or that it will let up in the years to come....