Disposable and discretionary income in the context of Personal consumption expenditures price index

The middle class refers to a class of people in the middle of a social hierarchy, often defined by occupation, income, education, or social status. The term has historically been associated with modernity, capitalism and political debate. Common definitions for the middle class range from the middle fifth of individuals on a nation's income ladder, to everyone but the poorest and wealthiest 20%. Theories like "Paradox of Interest" use decile groups and wealth distribution data to determine the size and wealth share of the middle class.

Terminology differs in the United States, where the term middle class describes people who in other countries would be described as working class. There has been significant global middle-class growth over time. In February 2009, The Economist asserted that over half of the world's population belonged to the middle class, as a result of rapid growth in emerging countries. It characterized the middle class as having a reasonable amount of discretionary income and defined it as beginning at the point where people have roughly a third of their income left for discretionary spending after paying for basic food and shelter.

In economics, the consumption function describes a relationship between consumption and disposable income. The concept is believed to have been introduced into macroeconomics by John Maynard Keynes in 1936, who used it to develop the notion of a government spending multiplier.

Major film studios are production and distribution companies that release a substantial number of films annually and consistently command a significant share of box office revenue in a given market. In the American and international markets, the major film studios, often known simply as the majors or the Big Five studios, are commonly regarded as the five diversified media conglomerates whose various film production and distribution subsidiaries collectively command approximately 80 to 85% of American box office revenue. The term may also be applied more specifically to the primary motion picture business subsidiary of each respective conglomerate.

Since the dawn of filmmaking, the major American film studios have dominated both American cinema and the global film industry. American studios have benefited from a strong first-mover advantage in that they were the first to industrialize filmmaking and master the art of mass-producing and distributing high-quality films with broad cross-cultural appeal. Today, the Big Five majors – Universal Pictures, Paramount Pictures, Warner Bros., Walt Disney Studios, and Sony Pictures – routinely distribute hundreds of films every year into all significant international markets (that is, where discretionary income is high enough for consumers to afford to watch films). The majors enjoy "significant internal economies of scale" from their "extensive and efficient [distribution] infrastructure," while it is "nearly impossible" for a film to reach a broad international theatrical audience without being first picked up by one of the majors for distribution. Today, all the Big Five major studios are also members of the Motion Picture Association (MPA) and the Alliance of Motion Picture and Television Producers (AMPTP).

Induced consumption is the portion of consumption that varies with disposable income. When a change in disposable income “induces” a change in consumption on goods and services, then that changed consumption is called “induced consumption”. In contrast, expenditures for autonomous consumption do not vary with income. For instance, expenditure on a consumable that is considered a normal good would be considered to be induced.

In the simple linear consumption function,