What would be the formula to calculate actual growth of product in a market, if they are growing at a different pace?

Question

If a product is growing at 5% and the market for which the product corresponds is growing at 12%, what is the formula to calculate what the actual growth is of that product?

Answer 1

Let M= Market and x be firm. X(t) = X(0)*e^xt and M(t)= M(0)e^mt

The Market Share S(t) =(X(0))/(M(0))e^(x-m)t or the market Share is decreasing at a 7% continuously compounded rate.