Pirate Island Threshold

The idea of the Pirate Island Threshold (or P.I.T - the sort you might bury treasure in, haha), is that in the eternal duel between Ninjas and Pirates, that Pirates win in sea-based battles, whilst Ninjas win land-based battles.

However, it is clear that Pirates do control some land - island upon which their treasure is buried, or ports with appropriate taverns.

A matter of size

So which islands to the pirates control?

• Indonesian islands
• Caribbean islands

In addition, I think it's fair to consider the Malay peninsula to be pirate territory.

On the other hand, Ninja's obviously control the island of Japan.

So what is the threshold of island size beyond which it is too big for pirates to control as a 'treasure island'?

Potential systems

Static Threshold?

There may be a simple island surface area beyond which pirate control is unsustainable, and ninja control is inevitable?

Variable Threshold (Tropical)

Pirates are able to control larger islands the closer they are to the equator. This is due to loose/open pirate garb being more suited to warmer climates than enclosed black ninja garb.

Variable Threshold (island topology)

Land area may not be as relevant as distance to shore... a long thin island (or peninsula - eg Malay) can be pirate controlled, whilst a smaller rounder island may still be viable Ninja land.