By Shashwat Chauhan Dec 11 (Reuters) - Canada's main stock index fell in broad-based declines on Monday with materials leading the selloff, while investors awaited a raft of economic data and decisions from major central banks due later in the week. More data gauging inflation in the United States, including November consumer prices, would be on the investors' watchlist ahead of the Fed's rate decision. Among individual stocks, BlackBerry BB.TO dipped 2.1% after the company shelved a plan to spin off its Internet of Things (IoT) business.