Sonja Lyubomirsky

American psychologist at UC Riverside — author of The How of Happiness — whose research on the determinants of happiness and the 40% solution (40% of happiness variance is within voluntary control) is foundational to positive psychology.

Developed the happiness pie chart — the finding that roughly 50% of happiness is set by genetics, 10% by life circumstances, and 40% by intentional activities — making happiness actionable by identifying the specific behaviors within voluntary control that move the needle.