What is a Value Stream Mapping?
Value stream mapping draws every step from request to delivered value, timing each one and — crucially — the waits between them. Each step is value-adding or waste; the ratio of value-add time to total elapsed time is usually a small, embarrassing number, and that embarrassment is the improvement roadmap.
Lean's founding insight applies: you don't speed up the work, you remove the waiting. Map first, then attack the longest queues.
Formula
Process efficiency = value-adding time ÷ total lead time
Worked example
Mapping "idea to production" at an insurer: coding 3 days, code review wait 4 days, security review queue 9 days, release train wait 6 days — 3 value days inside a 26-day pipe, 11% efficiency. Nobody codes faster; the security team embeds a reviewer instead, and the pipe drops to 9 days. The map found what no amount of "developer productivity" talk ever would.