The Imperial Standard Monster Danger Index is a continuous reference scale for estimating the potential risk posed by Monstrous Creatures to persons and materials traveling through the undeveloped regions of the world. The MDI uses two separate components: the Agergate Chalange Rating (ACR) of all common monster species within an area and the Standard Economic Development Index (SEDI) for the same area. MDI is derived by dividing the ACR by the SEDI.
The primary purpose of MDI is to determine the cost of Monster Insurance for residents within a region, as well as to determine the value of slain monsters from the region for the purposes of paying the monster's bounty to hunters.
Most Imperial settlements in the Homeland have an MDI between 1 and 2. Most regions of Eyom have an approximate rating of 3.
The MDI produces a decimalized number of either a positive or negative value. Unlike the majority of Imperial Rating Indexes, MDI does not use the Absolute Value of its ratings. A negative MDI rating is produced when both the local economy is unlikely to produce sufficient wealth to tame the wilderness, and the monsters within the local wilds are exceptionally dangerous. Therefore a negative MDI means the region in question is extremely hazardous and should not be considered for either insurance or bounty purposes. Negative MDI zones are often referred to as Negative Asset Regions.
For Posative MDIs, lower is safer, and higher is more dangerous. An MDI of zero is awarded only to locations that are comparable in safety to the Imperial Heartlands. In such locations, there is no inherent risk to communities from monsters and travel is perfectly safe so long as travelers heed all signs and read any literature provided by local rangers. MDIs above zero represent a geometrically increasing risk to people and property within a given region.
While MDIs can be rather high in dangerous regions, the functional difference in MDIs higher than 12 becomes academic. Consequently, MDIs are generally listed as a real number between zero and twelve, with any greater value listed as 12+. While the formal usage oF MDI for adjusting insurance and bounty payouts is nuanced and complex, the MDI is often used as a simple multiplier by younger clerks. Using MDI in this way is illegal as it will produce numbers outside of the 0.3% margin of error tolerance. For academic purposes, using MDI as a multiplier produces results averaging 0.5% lower than using the MDI correctly.
MDI ratings are usually delivered as their raw number, which is useful in insurance adjustment claims. Unofficial systems which simplify these numbers exist due to the MDI's use by other institutions. The most common rating system is the Guard's Rating, a system that maps the MDI number to one of five categories based on civil defense. The second most common alternative rating system is the Traveler's Lamp, which matches MDI ratings to six colors based on risk to travelers. The Traveler's Lamp misuses MDI by applying it to subregions in an attempt to rate specific areas and routs using MDI. While the Traveler's Lamp is used almost ubiquitously, it is not endorsed by any Imperial agency.