While the SCF data do not offer any definitive answers, they do give some previously unavailable insight into the role of creditworthiness, if we use changes in wealth as proxies for changes in creditworthiness. I want to apologize in advance.
I found that the rich data set offered some occasionally surprising insights into both of these questions, and I was unable to choose between the two topics. The result is a somewhat overpacked discussion. Despite that, I warn you: These results are the tip of a very large iceberg and may spur more questions than answers in your minds.