Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Year | Laureate | Relation | Category | Rationale |
| --- | --- | --- | --- | --- |
| 1922 | Otto Fritz Meyerhof | Research Professor in Physiological Chemistry, 1940–1951 | Physiology or Medicine | "for his discovery of the fixed relationship between the consumption of oxygen and the metabolism of lactic acid in the muscle" |
| 1938 | Richard Kuhn | Visiting Research Professor for Physiological chemistry | Physiology or Medicine | "for his work on carotenoids and vitamins" |
| 1955 | Vincent du Vigneaud | Assistant in Biochemistry, Graduate School of Medicine, 1924–1925 | Chemistry | "for his work on sulphur compounds, especially the first synthesis of a polypeptide hormone" |
| 1961 | Robert Hofstadter | Research Fellow, 1939–1940; Physics Instructor, 1940–1941 | Physics | "for his pioneering studies of electron scattering in atomic nuclei and for his thereby achieved discoveries concerning the structure of the nucleons" |
| 1964 | Martin Luther King, Jr. | Graduate Student, 1950–51 | Nobel Peace Prize | for being "the first person in the Western world to have shown us that a struggle can be waged without violence." |
| 1967 | Ragnar Granit | Research Fellow, 1929–1931; Sc.D., 1971 | Physiology or Medicine | "for their discoveries concerning the primary physiological and chemical visual processes in the eye" |
| 1967 | Haldan Keffer Hartline | Research Fellow in Biophysics, 1931–1936; Assistant Professor, 1936–1942; Associate Professor, 1943–1948; Professor, 1948–1949; Sc.D., 1971 | Physiology or Medicine | "for their discoveries concerning the primary physiological and chemical visual processes in the eye" |
| 1971 | Simon Kuznets | Assistant Professor of Economic Statistics, 1930–1934; Associate Professor, 1934–1935; Professor, 1936–1954; Sc.D., 1956; LL.D., 1976 | Economics | "for his empirically founded interpretation of economic growth which has led to new and deepened insight into the economic and social structure and process of development." |
| 1972 | Christian B. Anfinsen | M.S., 1939; Sc.D., 1973 | Chemistry | "for his work on ribonuclease, especially concerning the connection between the amino acid sequence and the biologically active conformation" |
| 1972 | Gerald Edelman | M.D., 1954; Sc.D., 1973 | Physiology or Medicine | "for their discoveries concerning the chemical structure of antibodies" |
| 1972 | John Robert Schrieffer | Professor of Physics, 1962–1980; Sc.D., 1973 | Physics | "for their jointly developed theory of superconductivity, usually called the BCS-theory" |
| 1976 | Baruch Samuel Blumberg | Professor of Medicine, 1964– ;Sc.D., 1990 | Physiology or Medicine | "for their discoveries concerning new mechanisms for the origin and dissemination of infectious diseases" |
| 1980 | Lawrence Klein | Professor of Economics, 1958– | Economics | "for the creation of econometric models and the application to the analysis of economic fluctuations and economic policies." |
| 1985 | Michael Stuart Brown | A.B., 1962; M.D., 1966; Sc.D. 1986 | Physiology or Medicine | "for their discoveries concerning the regulation of cholesterol metabolism" |
| 1997 | Stanley B. Prusiner | A.B., 1964; M.D., 1968 | Physiology or Medicine | "for his discovery of Prions - a new biological principle of infection" |
| 1999 | Ahmed Zewail | Ph.D., 1974; Sc.D. 1997 | Chemistry | "for his studies of the transition states of chemical reactions using femtosecond spectroscopy" |
| 2000 | Alan J. Heeger | Laboratory for Research on the Structure of Matter, 1962–1982 | Chemistry | "for their discovery and development of conductive polymers" |
| 2000 | Alan MacDiarmid | Department of Chemistry, 1955– ; Blanchard Professor of Chemistry, 1988– | Chemistry | "for their discovery and development of conductive polymers" |
| 2000 | Hideki Shirakawa | Department of Chemistry, Post-Doctoral Researcher, 1976 | Chemistry | "for their discovery and development of conductive polymers" |
| 2002 | Raymond Davis, Jr. | Professor, 1985–2006 | Physics | "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos" |
| 2004 | Irwin Rose | Professor of Physical Biochemistry, 1971– | Chemistry | "for the discovery of ubiquitin-mediated protein degradation" |
| 2004 | Edward C. Prescott | Assistant Professor, 1967–1971 | Economics | "for their contributions to dynamic macroeconomics: the time consistency of economic policy and the driving forces behind business cycles." |
| 2006 | Edmund Phelps | Professor, 1966–1971 | Economics | "for his analysis of intertemporal tradeoffs in macroeconomic policy." |
| 2008 | Harald zur Hausen | Assistant professor, 1968–1969 | Physiology or Medicine | "for his discovery of human papilloma viruses causing cervical cancer" |
| 2009 | George E. Smith | B.S., 1955 | Physics | "for the invention of an imaging semiconductor circuit – the CCD sensor" |
| 2009 | Oliver E. Williamson | Professor, 1965–1983 | Economics | "for his analysis of economic governance, especially the boundaries of the firm" |
| 2010 | Ei'ichi Negishi | Ph.D., 1963 | Chemistry | "for palladium-catalyzed cross couplings in organic synthesis" |
| 2011 | Thomas J. Sargent | Professor, 1970–1971 | Economics | "for their empirical research on cause and effect in the macroeconomy" |
Question:
how many laureates were in the field of physics?
Answer:
4