Does the U.S. Treasury actively manage the maturity structure of the national debt to minimize borrowing costs?

Evidence:

Maturity structure – 68 quarter end proportions of bills, notes, bonds as a percentage of total marketable debt. Combine amounts outstanding of Treasury inflation indexed notes and nominal notes. Combine amounts outstanding of Treasury inflation indexed bonds and nominal bonds, 2000.I through 2016.III

Cost:
Quarter end term spreads from data series GS1M, GS1, GS10.

State a testable hypothesis concerning this research question

Use the evidence to evaluate your testable hypothesis.

Produce a type written report no longer than 4 pages presenting testable hypothesis, summary statistics and other evidence directly related to your hypothesis, include references. State your conclusion and summarize your findings.