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Equation 1 · Part 5 · Reactor Phylogenetics: The Family Tree of Fission Power

Symbol a

P(next adopter=A∣nA,nB)=nA+anA+nB+a+bP(\text{next adopter} = A \mid n_A, n_B) = \frac{n_A + a}{n_A + n_B + a + b}
aa

What this part means

a is one of the signed contributions combined to compute the quantity on the left.

Its job in the formula

a is one of the signed contributions combined to compute the quantity on the left.

The passage around this formula

…by markets, regulators, and accidents is observably real and, in the case of TMI, Chernobyl, and Fukushima, dated and measurable. And the founder-effect and lock-in mechanism Cowan documents is not just analogous to a general economic idea — it is the same model. W. Brian Arthur’s 1989 formalization of competing technologies under increasing returns describes exactly this dynamic as a generalized Pólya urn: two technologies accumulate adopters, and the probability the next adopter chooses technology A over B…

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Learn the underlying idea

A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.

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Sources cited in the surrounding passage

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