In 1919, the first book on commercial research was published, "Commercial Research: An Outline of Working Principles" by Professor C.S. Duncan of the University of Chicago. Adequate knowledge of consumer preferences was a key to survival in the face of increasingly competitive markets. By the 1920s, advertising agencies, such as J Walter Thompson (JWT), were conducting research on the "how" and "why" consumers used brands, so that they could recommend appropriate advertising copy to manufacturers. The advent of commercial radio in the 1920s, and television in the 1940s, led a number of market research companies to develop the means to measure audience size and audience composition. In 1923, Arthur Nielsen founded market research company, A C Nielsen and over next decade pioneered the measurement of radio audiences. He subsequently applied his methods to the measurement of television audiences. Around the same time, Daniel Starch developed measures for testing advertising copy effectiveness in print media (newspapers and magazines), and these subsequently became known as Starch scores (and are still used today). During, the 1930s and 1940s, many of the data collection methods, probability sampling methods, survey methods, questionnaire design and key metrics were developed. By the 1930s, Ernest Dichter was pioneering the focus group method of qualitative research. For this, he is often described as the 'father of market research.' Dichter applied his methods on campaigns for major brands including Chrysler, Exxon/Esso where he used methods from psychology and cultural anthropology to gain consumer insights. These methods eventually lead to the development of "motivational research." Marketing historians refer to this period as the "Foundation Age" of market research. By the 1930s, the first courses on marketing research were taught in universities and colleges. The text-book, "Market Research and Analysis" by Lyndon O. Brown (1937) became one of the popular textbooks during this period. As the number of trained research professionals proliferated throughout the second half of the 20th-century, the techniques and methods used in marketing research became increasingly sophisticated. Marketers, such as Paul Green, were instrumental in developing techniques such as conjoint analysis and multidimensional scaling, both of which are used in positioning maps, market segmentation, choice analysis and other marketing applications. Web analytics were born out of the need to track the behavior of site visitors and, as the popularity of e-commerce and web advertising grew, businesses demanded details on the information created by new practices in web data collection, such as click-through and exit rates.