structural:summarization, structural:scholar_edition, information:classification
20th century

At the turn of the twentieth century, the need for skilled and trained managers had become increasingly apparent. The demand occurred as personnel departments began to expand rapidly. In 1915, less than one in twenty manufacturing firms had a dedicated personnel department. By 1929 that number had grown to over one-third. Formal management education became standardized at colleges and universities. Colleges and universities capitalized on the needs of corporations by forming business schools and corporate placement departments. This shift toward formal business education marked the creation of a corporate elite in the US.

By about 1900 one finds managers trying to place their theories on what they regarded as a thoroughly scientific basis (see scientism for perceived limitations of this belief). Examples include Henry R. Towne 's Science of management in the 1890s, Frederick Winslow Taylor 's The Principles of Scientific Management (1911), Lillian Gilbreth 's Psychology of Management (1914), Frank and Lillian Gilbreth 's Applied motion study (1917), and Henry L. Gantt 's charts (1910s). J. Duncan wrote the first college management textbook in 1911. In 1912 Yoichi Ueno introduced Taylorism to Japan and became the first management consultant of the " Japanese management style ". His son Ichiro Ueno pioneered Japanese quality assurance.

The first comprehensive theories of management appeared around 1920. The Harvard Business School offered the first Master of Business Administration degree (MBA) in 1921. People like Henri Fayol (1841–1925) and Alexander Church (1866–1936) described the various branches of management and their inter-relationships. In the early 20th century, people like Ordway Tead (1891–1973), Walter Scott (1869–1955) and J. Mooney applied the principles of psychology to management. Other writers, such as Elton Mayo (1880–1949), Mary Parker Follett (1868–1933), Chester Barnard (1886–1961), Max Weber (1864–1920), who saw what he called the "administrator" as bureaucrat, Rensis Likert (1903–1981), and Chris Argyris (born 1923) approached the phenomenon of management from a sociological perspective.

Peter Drucker (1909–2005) wrote one of the earliest books on applied management: Concept of the Corporation (published in 1946). It resulted from Alfred Sloan (chairman of General Motors until 1956) commissioning a study of the organization. Drucker went on to write 39 books, many in the same vein.

H. Dodge, Ronald Fisher (1890–1962), and Thornton C. Fry introduced statistical techniques into management studies. In the 1940s, Patrick Blackett worked in the development of the applied-mathematics science of operations research, initially for military operations. Operations research, sometimes known as " management science " (but distinct from Taylor's scientific management), attempts to take a scientific approach to solving decision problems and can apply directly to multiple management problems, particularly in the areas of logistics and operations.

Some of the later 20th-century developments include the theory of constraints (introduced in 1984), management by objectives (systematized in 1954), re-engineering (the early 1990s), Six Sigma (1986), management by walking around (1970s), the Viable system model (1972), and various information-technology -driven theories such as agile software development (so-named from 2001), as well as group-management theories such as Cog's Ladder (1972) and the notion of "thriving on chaos" (1987).

As the general recognition of managers as a class solidified during the 20th century and gave perceived practitioners of the art/science of management a certain amount of prestige, so the way opened for popularised systems of management ideas to peddle their wares. In this context, many management fads may have had more to do with pop psychology than with scientific theories of management.

Business management includes the following branches: