Let's write a tautology : A = A
Let's rewrite it : A = A/B * B<p>Now, I often see people (in economics, mostly) do this little trick :<p>ΔA = Δ(A/B * B)
Δ * ln(A) = Δ * ln(A/B) + Δ * ln(B)<p>Then, they will show that, empirically, A/B has always been constant (more or less), thus, if you want to increase A, you just have to work on increasing B.<p>Can this kind of equation actually say something about reality ?
Can it be falsified, so it can be taken seriously to be used for predictions ?<p>(to add some context, I'm thinking here about Kaya identity)