The Globe and Mail reports in its Friday, Sept. 26, edition that Constellation Software chief executive officer Mark Leonard has resigned for health reasons, concluding a three-decade career as a prominent Canadian company builder. The Globe's Sean Silcoff and Tim Kiladze write that Mr. Leonard, who is in his 60s, is being replaced by chief operating officer Mark Miller, an early Constellation employee. Mr. Leonard will remain a board director. Constellation shares are down 12.45 per cent since the start of the year, while the S&P/TSX Composite Index has gained 20.2 per cent over that period. Mr. Leonard said he had "complete confidence" in Mr. Miller to lead the company. BMO Capital Markets analyst Thanos Moschopoulos called Mr. Leonard "irreplaceable" in a note but added that the company's "highly decentralized structure and bench strength should mitigate the impact associated with this transition." Before this year, Constellation was one of the fastest-growing companies on the Toronto Stock Exchange, averaging over 30-per-cent annual returns since going public in 2006. Mr. Leonard built Constellation into a technology juggernaut with a disciplined approach, buying well over 1,000 software companies.