with whom one can maintain stable social relationships. No precise value has been proposed for Dunbar's number, but a commonly cited approximation is 150. First proposed by British anthropologist Robin Dunbar. Dunning–Kruger effect is a cognitive bias in which people who are unskilled in some area wrongly believe their ability is higher than average; they don't know enough about the subject to accurately measure their aptitude. People with well-above-average skills are acutely aware of how much they don't know of the subject, but less aware of the general ineptitude of others, so tend to underestimate their relative ability. Duverger's law: Winner-take-all (or first-past-the-post) electoral systems tend to create a two-party system, while proportional representation tends to create a multiple-party system. Named for Maurice Duverger. E–G Edholm's law predicts that bandwidth and data rates double every 18 months. Named for Phil Edholm. Einasto's law relates the density of a galaxy to distance from the center. Named for Jaan Einasto. Elliott wave principle is a form of technical analysis that finance traders use to analyze financial market cycles and forecast market trends by identifying extremes in investor psychology, highs and lows in prices, and other collective factors. Named for American accountant Ralph Nelson Elliott. El-Sayed rule, in physical chemistry states that "the rate of intersystem crossing (same energy radiationless transition between two electronic states), e.g. from the lowest singlet state to the triplet manifold, is relatively large if it involves a change of molecular orbital type" Emmert's law, in optics: objects that generate retinal images of the same size will look different in physical size (linear size) if they appear to be located at different distances. Named for Emil Emmert. Engelbart's law: "The intrinsic rate of human performance is exponential." Eroom's law, the observation that drug discovery is becoming slower and more expensive over time, despite improvements in technology. The name "Eroom" is "Moore" spelled backward, in order to contrast it with Moore's law. Euler's laws of motion: extends Newton's laws of motion for point particle to rigid body motion. Faraday's law of induction: a magnetic field changing in time creates a proportional electromotive force. Named for Michael Faraday, based on his work in 1831. Faraday's law of electrolysis: the mass of a substance produced at an electrode during electrolysis is proportional to the number of moles of electrons transferred at that electrode; again named for Michael Faraday. Faxén's law: In fluid