Conversation so far:
Where did Murray Rothbard go to school?
Murray Rothbard attended Birch Wathen, a private school in New York City.
Did Murray Rothbard study anywhere else besides Birch Wathen?
Murray Rothbard attended Columbia University.
What did Murray Rothbard study at Columbia University?
Murray Rothbard received a Bachelor of Arts degree in mathematics in 1945 and eleven years later his PhD in economics in 1956.
Did Murray Rothbard do any research?
The delay in receiving his PhD was due in part to conflict with Murray Rothbard's advisor, Joseph Dorfman, and in part to Arthur Burns’s rejecting his doctoral dissertation.
What did Murray Rothbard do after his time in college?
Murray Rothbard attracted the attention of the William Volker Fund, a group that provided financial backing to promote various right-wing ideologies.

Question: How long did he stay there?
Self-contained rewrite: How long did Murray Rothbard stay with the William Volker Fund?