A trader works on the floor of the New York Stock Exchange (NYSE) in New York.

Last month was one for the Wall Street history books — not only was it stocks' worst December since the Great Depression, but it now appears to be a pivotal moment when investors really gave up on active management.

According to data from Morningstar out Thursday, actively managed mutual funds experienced outflows of nearly $143 billion in December, their worst month ever. The record exodus brought the yearly outflows to $301 billion, just shy of 2016's $320 billion.

"December outflows spanned asset classes, with taxable-bond funds faring worst. [Active] large-growth and large-value funds continue to get hit the hardest, likely losing assets to passively managed, core large-blend funds," Morningstar senior analyst Kevin McDevitt said in a note on Thursday.