Voltage effect

What it means

The voltage effect names what happens to an intervention's effect size at scale: a 'voltage drop' is the common collapse of promising pilot results when a program expands, while occasionally voltage can rise. List identifies recurring causes of the drop — false positives in the original evidence, non-representative populations or settings, effects that depended on unscalable ingredients (a charismatic deliverer, a unique site), spillovers, and supply-side constraints as the program grows. The practical lesson is to interrogate scalability before scaling: test for false positives, use representative samples, and identify which active ingredients will survive expansion. It connects directly to the megastudy and translational-gap literatures, where modest, fragile effects are the norm. It matters because policymakers and firms routinely over-extrapolate from pilots, pouring resources into rollouts that fizzle — the gap between 'it worked here' and 'it works everywhere' is where most good ideas die.