D’oh : The city Independent Budget Office last week confirmed the obvious: When a homeless shelter opens up nearby, property values drop.

Obvious, that is, to everyone except Mayor Bill de Blasio and his minions — an obliviousness that explains why Manhattan Borough President Gale Brewer asked the IBO to put numbers on common sense.

Using data from the departments of Homeless Services and Finance, and controlling for other factors that influence prices, the IBO found that a home within 500 feet of a shelter for adults sells for 7.1 percent less than one further away; a shelter for families with kids cuts the price by 6.4 percent.

The problem for the mayor is that he has pledged to build 90 new shelters across the city, and wants to pretend that his targeted neighborhoods won’t suffer for it. So de Blasio spokeswoman Avery Cohen was obliged to denounce the IBO report, claiming it “is not only wrong on the facts, it’s morally indefensible.”

Not that she cited any false facts, or explained how recognizing reality is immoral.

Brewer, who’s plenty progressive herself, simply noted, “Facts unearthed by solid research like this are what public policy should be based on.” Good luck selling that approach to this mayor.