There is a direct proportion between two values when one is a multiple of the other. For example, \(1\text{cm} = 10\text{mm}.\) To convert \(\text{cm}\) to \(\text{mm}\), the multiplier is always 10.

Perold, André, and Fischer Black. "Theory of Constant Proportion Portfolio Insurance." Journal of Economic Dynamics & Control 16, nos. 3-4 (July–October 1992): 403–426.

In this graph, 𝑥 and 𝑦 are directly proportional. This means that when 𝑥 doubles, 𝑦 also doubles, and when 𝑥 triples, so does 𝑦. In fact, for all coordinates on this line, you could multiply or ...

ABN Amro’s constant proportion dynamic obligation deal was somewhat fittingly called Surf as it created a wave of curiosity, controversy and copycat transactions. Dealer and investor interest was ...