Relationship between usage rate and programme cost effectiveness when programme cost is constant. The figure illustrates how cost effectiveness changes depending on how frequently nets are used. The base case is 50% usage among the general population and 70% among under 5s, which gives LLIN cost effectiveness as USD 0.86 per person protected and USD 3.06 per under-5 protected. If conventional nets are used instead (with the same physical lifespan and purchase price and base case assumptions about retreatment), cost effectiveness is USD 1.16 per person protected. A higher usage rate implies a lower cost per person protected.