Planetary Development Scale

The Planetary Development Scale, or the Planet Class, or simply the PDS-score, indicated the development score of a planet. This score was distributed on a 0-10 scale, where 0 represented an uninhabited planet and 10 being a theoretical ecumenopolis.

The score
The score was calculated by taking various factors into account. These factors included but were not limited to:
 * Permanent population of a planet
 * Diversity in races in the population
 * United planetary government
 * Percentage of buildable area being an urban area
 * Economic power of a planet
 * Cultural power of a planet
 * Technological power of a planet
 * Military power or strategic importance of a planet.

The Scale
The score was distributed on a 0-10 scale, where 0 indicated that the planet was completely uninhabited. A score of 9 and 10 indicated planetary development that was comparable with an ecumenopolis, a planet that was covered in urban area. No such planets exist in known space, although it is speculated that the Vrox homeworld is likely to be in the 9 or 10 PDS range. Another candidate is N'Krek, the Nork homeworld. Its score is being debated by scientist and cultural observers throughout the galaxy.

Elaboration on the different scores
0: Planets with this score are not inhabited. For a planet to have a score of 0, it must at least be theoretically possible for any known sentient race to live on the planet for at least a decade.

1: Planets with this score are barely colonies. The settlements are very minor, and the total planetary population is under 500 souls.

2: Planets with this score are stable minor colonies. Towns are emerging, and the total planetary population is usually between 500 and 50.000 souls.

3: Planets with this score house at least one minor city. The total planetary population is usually between 50.000 and 500.000 souls.

4: Planets with this score house at least one significant urban center. The total planetary population is usually between 500.000 and 5 million souls. PDS-4 planets usually start having a strong enough economy to start exploiting their solar system, provided that no other PDS-4 or higher planets are present.

5: Planets with this score start to matter somewhat on galactic scale. The total planetary population is usually between 5 million and 500 million. PDS-5 planets usually have the economic power to dominate their solar system, provided that no PDS-5 or higher planets are present. Most PDS-5 planets have their own dedicated spaceport.

6: Planets with this score are known players in the galaxy. The total planetary population is usually between 500 million and 3 billion. These planets usually are able to provide everything their citizens need to survive their entire natural life. Metropolitarian areas are plentiful on the planets surface.

7: Planets with this score start to be powerful forces in the galaxy, and renown hubs of commerce and culture. The planetary population is between 3 billion and 15 billion. Planets of this scale are highly urbanised but still have room for nature. Excellent planetary and orbital infrastructure, as well as extensive economic power, is associated with this scale. Megalopolisian areas are emerging on the planets surface.

8: These planets are the powerhouses in the Galaxy, and dominate their respective nations. The planetary population is between 15 billion and 40 billion. Megalopolisian areas dominate the planets surface, and extensive areas of nature are rapidly getting rare.

9: Development on this scale is currently theoretical. The population of the planet would between 40 billion and well into the 1 trillion. Almost the entire planet would be covered in a interconnected dense urban area. The planet would sport such extensive orbital infrastructure that the difference between planet and space would only be the atmosphere.

10: Development on this scale is currently theoretical. The population of such a planet would be well into the trillions of souls. The entire planet is covered in a highly interconnected urban area. This urban area would likely be divided up in multiple ground floors as entire urban districts are built on top of each other. The border between planet and space would be fuzzy in some places.

Trivia

 * It is speculated that the Vrox homeworld has a PDS of 9 or possibly even 10.
 * No planets in known space have a rating higher than 8. However, Earth is projected to be the first to eventually reach the rating of 9 thanks to its ever-growing planetary growth and development.
 * Planets under control of the Nork Collectiveness have no official rating, as they are all controlled by a single hive mind.
 * Concordia and Urseario are the only known planets to have a drop in their rating. Concordia's rating dropped during the Vrox Rampage. Urseario's rating temporarily dropped significantly, going from 8 to 0 after the Nova of Saris. (Or possibly 1, as it is unclear wether there were any survivors that continuously lived on Urseario for a decade after the Nova.)