The appropriate interest rate depends not only on the level of inflation, but also on the amount of slack in the economy.

ECONOMIST: American interest rates need to rise

Interest at the appropriate underpayment rate must be paid on tax payments received after November 16, 2011.

FORBES: New Yorkers Get More Tax Time For Snow

As an example with a low interest rate environment adding long bonds may not be appropriate when interest rates go up.

FORBES: A Hot Investment Recommendation

If enough persons want to own T-bills at any price, even at a negative rate of interest, then THAT is the appropriate price at which the bill should trade.

FORBES: Negative Treasury Bill Rates Are On The Way

In an address to the European Parliament, Mr Duisenberg said the bank had no reason to change its view that its current benchmark interest rate - currently at 4.5% - was appropriate.

BBC: ECB: European interest rates 'appropriate'