The composition of a company's mixture of debt and equity financing. A firm's debt-equity ratio is often referred to as its gearing. Taking on more debt is known as gearing up, or increasing lever age. In the 1960s, Franco Modigliani and Merton Miller (1923–2000) published a series of articles arguing that it did not matter whether a company financed its activities by issuing debt, or equity, or a mixture of the two. (For this they were awarded the Nobel Prize for economics. ) But, they said, this rule does not apply if one source of financing is treated more favourably by the taxman than another. In the United States, debt has long had tax advantages over equity, so their theory implies that American firms should finance themselves with debt. Companies also finance themselves by using the profit they retain after paying dividends.