The standard measure is gross value-added the output of an industry minus the costs of production.

ECONOMIST: The banks' contribution to the economy has been overstated

Gross value added is calculated at the level of branches of the economy as the value of output of goods and services less the value of intermediate consumption.

UNESCO: Belarus: Report: Part I: Descriptive Section

It has adjusted UK gross value added, a measure of economic output, to exclude energy extraction and use, and also financial and insurance activities.

BBC: How pretty is the UK without the "bad bits"?