A significant theme you need to find in stocks is sustainability: Needham's Chris Retzler

Chris Retzler, Needham small cap growth fund portfolio manager, and Brian Nick, Nuveen chief investment strategist, join 'Squawk Alley' to discuss if they think the tech names that led the market in 2020 will continue to lead in 2021 and how the transition between President Trump and President-elect Biden will affect markets. A significant theme you need to find in companies, says Retzler, is sustainability. What were the trends before the pandemic? What are the trends after the pandemic?