A pasture that belongs to everyone tends to be grazed until it is ruined. Each herder coll the wh benefit o adding o more ani, yet abs only a frac of t damage do to t pasture. The arithmetic pushes every reasonable herder toward expansion, although all of them together destroy the resource. Economists call this a collective action problem, and it appears wherever a benefit is private while the cost is shared. Fisheries, aquifers and clean air obey the same unforgiving logic.

Type only the missing letters. Each box is one letter, and the number of boxes matches the letters that are missing.