Levi's CEO fired more than half of his execs during his first 18 months in the role and regrets not letting go of some staff more quickly

• Levi's boss Charles Bergh has discussed his hiring and firing strategy at the company.
• Bergh became CEO of Levi's in 2011 at a time when sales and brand loyalty were faltering.
• "The easiest way to change the culture is to change the people," Bergh told CNBC in an interview.

The CEO of Levi Strauss & Co said he took a hardline approach when it came to firing people.