The WDMMA annual ranking utilizes a formula which takes into account values related to total fighting strength of the various air services of the world. The formula produces the 'TrueValueRating' (TvR) helping to definitively separate each power based on - not only overall strength - but modernization, logistical support, attack and defense capabilities an so on. In this way, a power is not simply assessed on its total quantity of aircraft but rather its quality and general mix of inventory. TvR remains, however, a work-in-progress and is constantly revaluated as needed. Greater weight is given to categories generally overlooked by some powers, namely special-mission, dedicated bomber force, CAS, training, and on-order units. Beyond this is a focus on local aero-industry capabilities, inventory balance (general mix of unit types), and force experience.
The highest attainable TvR score is 242.9 held by the United States Air Force (USAF). The USAF features a broad mix of aircraft types as well as balance strengthened by overall numbers (quantity). Many of its products are locally-sourced thanks to the U.S.'s massive industrial base. It also maintains dedicated strategic-level bombers, CAS aircraft, a sizeable helo and fighter force (of which many are multirole types), and hundreds of transport aircraft to reach anywhere in the world. Beyond this is a large training, tanker, and special-mission force. The service is also set to be reinforced in the near-future with hundreds of units still on-order.
The current WDMMA inventory consists of 71 countries tracked, 97 air services covered (this includes Army, Navy, and Marine branches of service where applicable), and 45 total aircraft followed.