Ken Griffin's Citadel is cashing in on the day-trading boom by buying customers' orders

· *Ken Griffin's Citadel Securities is cashing in on the day-trading boom, the Financial Times reported on Monday.*
· *The market maker handles 40% of shares traded by individual investors in the US, the newspaper said.*
· *Citadel has benefited from a surge in retail investing fueled by the advent of zero-commission trading...