The government isn't selling them anymore. One-year bills won't come back as long as the national debt keeps going down. The change was announced on Jan. 31, although you might not have heard about it. The last auction of one-year bills was held on Feb. 27. But instead of being a real rate, it will be inferred from other rates.
Investors can use it to measure the risk-free rate in the marketplace.
You'd expect a one-year investment to pay more than the Treasury rate. The government will also use the constant maturity rate as a benchmark for its variable-rate loans. For example, it will establish what students pay for subsidized student loans. So you'll see references to the one-year rate, even though that bill doesn't exist anymore. That's the most likely place for today's one-year investors to move.