Are non-renewable resources becoming more or less substitutable by other productive inputs with the passage of time?

Question:

Are non-renewable resources becoming more or less substitutable by other productive inputs with the passage of time? What are the possible implications for efficient resource use of the elasticity of substitution between non-renewable resources and other inputs becoming

(a) higher, and

(b) lower with the passage of time?

Fantastic news! We've Found the answer you've been seeking!