What is a Fixed Formula Method (50/50 Rule)?
The fixed formula method credits earned value in preset chunks: 50/50 (half when the activity starts, half at completion), 25/75, or 0/100 (nothing until done). It removes the most gameable number in project controls — subjective percent complete — from short activities where guessing adds nothing.
Choose by duration and temperament: 0/100 is the most conservative and suits activities within one or two reporting periods; 50/50 smooths the curve; subjective percent complete stays for long activities with measurable interim progress.
Formula
EV = start % × budget at start + remaining % × budget at completion
Worked example
A telecom rollout has 800 similar site installations of 3–5 days each. Asking supervisors for percent complete on each would generate 800 optimistic guesses weekly. The controls lead applies 0/100: a site earns value when it's integrated and passing traffic, period. The EV curve turns lumpy and honest — and the "94% complete for six weeks" site can no longer hide.