4 Houtenville and Conway (2008) note thatschool resources and parental inputs may be substitutes in education production.
However, as argued above,h and s may be substitutes in production, so thatthe marginal product of h is reduced when s increases,and vice versa.4.
Therefore, the search for eco-friendly, renewable energy resources that may be substitutes for fossil fuels has become indispensable for a sustainable future.
The decline of sea otters followed a decline in harbour seal and Steller sea lion populations, the killer whale's preferred prey, which in turn may be substitutes for their original prey, now decimated by industrial whaling.
We used a combined HMO and PPO measure following the conceptual argument that HMO and PPO may be substitutes so that they should be considered in the same relevant product market [ 34, 35].
This suggests that medical treatment and absences may be substitutes and that the behaviors of working men and non-working married women may vary according to their healthcare choice.
