A central bank digital currency would take years to develop if the United States decided to issue one, Treasury Secretary Janet Yellen said Thursday, noting that she feels “urgency” in the need to push ahead with study on the issue. Her remarks came as President Joe Biden signed an executive order last month that calls for a government study on the possibility of issuing such a currency, known as a CBDC, through an assessment of the risks and benefits of doing so. “I can’t tell you yet the conclusions we will reach, but we must be clear that issuing a CBDC would likely present a major design a…