liability partnership can largely operate autonomously with regard to cultivating new business and servicing existing clients within their book of business. Partner compensation methods vary greatly among law firms. At major United States law firms, the "compensation spread" (ratio between the highest partner salary and lowest partner salary) among firms disclosing information ranges from 3:1 to 24:1. Higher spreads are intended to promote individual performance, while lower spreads are intended to promote teamwork and collegiality. Many large law firms have moved to a two-tiered partnership model, with equity and non-equity partners. Equity partners are considered to have ownership stakes in the firm, and share in the profits (and losses) of the firm. Non-equity partners are generally paid a fixed salary (albeit much higher than associates), and they are often granted certain limited voting rights with respect to firm operations. The oldest continuing partnership in the United States is that of Cadwalader, Wickersham & Taft, founded in 1792, in New York City. The oldest law firm in continuous practice in the United States is Rawle & Henderson, founded in 1783, in Philadelphia. Termination of one's partnership It is rare for a partner to be forced out by fellow partners, although that can happen if the partner commits a crime or malpractice, experiences disruptive mental illness, or is not contributing to the firm's overall profitability. However, some large firms have written into their partnership agreement a forced retirement age for partners, which can be anywhere from age 65 on up. In contrast, most corporate executives are at much higher risk of being fired, even when the underlying cause is not directly their fault, such as a drop in the company's stock price. Worldwide, partner retirement ages can be difficult to estimate and often vary widely, particularly because in many countries it is illegal to mandate a retirement age. "Of counsel" role In the United States, Canada and Japan, many large and midsize firms have attorneys with the job title of "counsel", "special counsel" or "of counsel." As the Supreme Court of California has noted, the title has acquired several related but distinct definitions which do not easily fit into the traditional partner-associate structure. These attorneys are people who work for the firm, like associates, although some firms have an independent contractor relationship with their counsel. But unlike associates, and more like partners, they generally have their own clients, manage their own cases,