The Arithmetic of Productivity Boosts: Why Does a “40% Increase in Productivity” Never Actually Work?

Productivity claims like '40% more productive' are often misleading because they optimize a small slice of total work time. Using a data scientist as an example, if model parameter selection takes only 4% of total work time, a 20% improvement there yields less than 1% overall gain. Marketing reframes narrow improvements as global productivity boosts. A more honest and useful metric is cognitive load reduction, which may not speed up tasks but preserves mental energy for sustained effective work.