From Reuven Glick and Kevin Lansing, Consumers and the Economy: Household Credit and Personal Saving:
In the years since the bursting of the housing bubble, the personal saving rate has trended up from around 1% to around 6%, while the ratio of household debt to disposable income has dropped from 130% to 118%. Changes over time in the availability of credit to households can explain 90% of the variance of the saving rate since the mid-1960s, including the recent uptrend, according to a simple empirical model.