You can calculate a stream of earnings off the asset, apply an assumed discount rate and determine a present value for the assets.

FORBES: What Exactly Does Michael Dell Have to Sell?

Interest rates are used to discount those cash flows and calculate their present value.

ECONOMIST: The ultimate measure by which a company is judged

Three factors determine the health of any pension fund: asset returns, company contributions and the discount rate, which is used to calculate the present value of pension liabilities and is tied to interest rates.

FORBES: GM Loosening The Noose From Its Massive Pension Plan