← All parts of this equation

Equation 5 · Part 9 · Selection Accounting: The Price Equation Runs the Economy

subscript

dzˉdt∣selection=β Var⁡s(z)\frac{d\bar z}{dt}\Big|_{\text{selection}} = \beta \, \operatorname{Var}_s(z)
subscript

What this part means

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

Its job in the formula

A subscript distinguishes a version, component, step, or member of a quantity. It does not automatically mean multiplication.

The passage around this formula

Add one falsifiable assumption — that market share evolves under replicator dynamics with a linear selection gradient linking a firm’s productivity advantage to its realized share growth — and Proposition 2 states an economic reading of Fisher’s fundamental theorem of natural selection [ 2 ] : dzˉdt∣selection=β Var⁡s(z)\frac{d\bar z}{dt}\Big|_{\text{selection}} = \beta \, \operatorname{Var}_s(z). The selection component of the growth rate of mean log productivity equals a selection-intensity coefficient β\beta times the share-weighted variance of log productivity across firms. The qualitative move is not new: Metcalfe applied Fisher’s principle to competing firms under replicator dynamics in the 1990s [ 4 ] , and Andersen used Price’s equation itself, by name, to split…

Read this part in the article →

Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

Open the illustrated subscripts: which member of a family? guide →

Sources cited in the surrounding passage

These citations provide research context; check each source for the exact claim it supports.