Trade-offs make a position sustainable because more of one thing means less of another. They arise from inconsistencies in image or reputation, from the activities themselves, and from limits on internal coordination. Continental Lite tried to straddle Southwest's position while staying full-service and lost hundreds of millions. The essence of strategy is choosing what not to do.

Fit among activities drives advantage and sustainability:

First-order: simple consistency with the strategy (Vanguard's cost focus everywhere)
Second-order: activities reinforce each other (Neutrogena's hotel and doctor marketing)
Third-order: optimization of effort (Gap restocking daily from warehouses)

Matching a whole system is far harder than one activity: 0.9 x 0.9 x 0.9... Positions should last a decade. The growth trap (Maytag) blurs positions; leaders must say no.