michael spencer the billionaire behind one of the world’s biggest financial brokerage fortunes cut his stake in cme group inc as its shares rebounded following the global outbreak of covid19 between early 2020 and 2021 the nex group plc founder’s family office sold more than 410000 cme shares that could have been worth about 90 million a uk registry filing showed this month the securities rose as much as 43 in that period rebounding after an initial plunge when the virus crisis started