There’s been a lot of talk about the need to achieve herd immunity, the point at which so many people are immune to a disease that it can no longer easily spread and the whole population is protected. If we can just hit that number, the thinking is, the country will be safe to reopen. But there is no one magic number. On today’s show: the challenges of reaching herd immunity and reopening. Plus, appliance shortages are holding up home improvement and construction, why retailers are opening so many brick-and-mortar stores this year and a look at racism in the tax code.