An unprecedented number of metro Denver home sellers pulled their listing off the market last month, while thousands went the other way, rushing to list their homes before a major economic downturn made a sale tougher to achieve. “How quickly our world has changed,” Jill Schafer, chair of the market trends committee at the Denver Metro Association of Realtors, said in comments accompanying the association’s monthly update. At the start of March, the metro Denver real estate market looked like it would launch into one of ts best spring-selling seasons ever — until efforts to contain the novel coronavirus caused the economy to grind a halt. Open houses became taboo, and showings became a virtual affair.