How big a whack did your credit score take during the grim years of economic distress following the housing bust? Was it 20 points, 50 points, 100 points — or maybe no drop at all? These are key questions affecting millions of potential home buyers who hope to qualify for mortgages as well as current owners looking to refinance. New research from a major credit-risk evaluation company suggests that the drop in huge numbers of Americans’ scores was dramatic.