Tag Archives: Population

People, People Everywhere (High Population Worlds, Part 1)

One thing you will remember from when we looked at the dice results for this sector was the insanely high total population – 2663 billion people – for what is supposed to be frontier-ish.

This is really due to four population code B worlds – that is, 100 billion or more inhabitants. I’ve already downgraded one of them. In addition, the sector contains 8 worlds inhabited by between 10 and 100 billion people:

(5)Temperate 1429 AA8ABB9-G Hi Ht Wa     HI5 834.000.000.000 (5)Temperate
(8)Temperate 0516 A763BD9-C Hi Ht       HI8 482.000.000.000 (8)Temperate
(3)Temperate 2614 BAA5BD9-7 Fl Hi       HI3 (3)Temperate
(8)Temperate 2917 B888AA9-7 Ga Hi       HI8 95.700.000.000 (8)Temperate
(3)Temperate 2611 A400A96-D Hi Ht In Na Va HI3 (3)Temperate
(8)Temperate 1418 C785A96-8 Ga Hi       HI8 61.700.000.000 (8)Temperate
(7)Temperate 2135 B784A89-7 Ga Hi       HI7 (7)Temperate
(5)Temperate 1113 A8A5A89-D Fl Hi Ht     HI5 30.500.000.000 (5)Temperate
(4)Hot 1935 B743A88-9 Hi In Po     HI4 15.700.000.000 (4)Hot
(3)Temperate 0305 B410AD9-B Hi In Na     HI3 (3)Temperate
Xoth 2219 A576A85-A Ga Hi In     HI7 (7)Temperate

Is this even possible?

From a pure math standpoint, absolutely. Earth’s population has increased dramatically over the past few centuries, as better agriculture and medicine reduced mortality – especially child mortality. When I was a kid, the world’s population hit 5 billion people. I remember the TV gala; for some weird reason people actually celebrated it. 2011, it was at 7 billion. Call it 25 years for 50% growth. Simply continue to feed all these people and you’ll have run-away, exponential growth.

Earth's Population over time, in Billion
Earth’s Population over time, in Billion

Of course, things aren’t as simple as that. First off, the Earth is a closed system and at some point – we are not sure where it would be – there simply won’t be enough food, energy and water. Population would hit a wall and things would turn ugly.

In reality, even if there was no limit to food, energy and water (say because of interstellar imports)  it won’t work out that way.

People adapt to their environment – we’re really good at that. Better health, more wealth, and especially better education also limit fertility. Women simply give birth to fewer children. In the 1950s, it was 5 kids per woman. In the early 2000s, it was half that. The UN expect it to eventually drop to just above 2.05. In other words, a balance will set in, and the best guesses place this at ~9 billion people.

A regular Sunday shopping in Chennai. A good example of the sea of humanity. cc-by-sa, McKay Savage
A regular Sunday shopping in Chennai. A good example of the sea of humanity. cc-by-sa, McKay Savage

In other words, a super-densely populated world isn’t going to happen in any natural way. Population growth is a byproduct of technological progress. If that progress stops, or even reverses, the population becomes unsustainable and will either crash or find an equilibrium. If technological progress continues unabated, then attitudes will change with it and population will find an equilibrium eventually as well, just at a higher level. To put it bluntly, people simply have better things to do with their lives than to raise kids continuously.

Genre Considerations

I am obviously not worried as much about building a realistic population model as I am about creating a setting that fits its genre and is internally consistent and, well, hopefully interesting.

Massively populated worlds are definitely in-genre. Asimov’s Trantor is of course the grand-daddy of them all, and had anything between 40-500 billion inhabitants. Coruscant has a trillion inhabitants. Then there are the many city-worlds of the Warhammer 40k empire (and probably others). Massive, galactic-scale societies support these worlds and absorb their effect on the economy.

In Niven’s “Known Space”, Earth has a population of 18 billion and is described as a crowded hell. Heinlein assumes 11 billion in “The Moon is a Harsh Mistress” and it’s not exactly doing us any good. (Of course in “Starman Jones”, Heinlein assumes that 4 billion people are a lot). In both cases, space travel is fairly limited for various reasons – all those Terrans can’t just mass-emigrate, which limits the effect on other worlds.

The World-Builder’s Solution

My gut reaction was to simply downgrade these worlds – as I did with #2021. However, I reminded myself of the reasons for using a random generator in the first place: It is supposed to spur our imagination, right?

Here’s a map of where those >1 billion people planets are:


The 1.2 in Subsector K is our world #2021, which originally had 786 billion people. Okay, so the absolute numbers are quite too high. But do you notice what I am seeing?

Subsector H, birthplace of the rebellion, has two super-high population planets. Lots of cheap manpower for the war. And that subsectors H-J axis I mentioned? Another super-high population world in subsector J – and the world with the highest tech level in the entire sector! Now, the 834 billion (and 482 billion) are just ridiculously high numbers, but if we fix it like so:


We’ve effectively preserved the random generator results, improved them significantly, and used them to explain the campaign’s political situation.

This brings the population of the sector down to 508 billion people – a fifth of what it was initially.

Next up, we’ll take a look at these planets’ individual UWPs to figure out just how these people might be living.


Now we’re getting to the really interesting bits: Populating all those worlds. In the standard Traveller system, Population size is simply rolled with 2d6-2. The “hard science” rules add the following modifiers:

  • If Size is 0–2 (low gravity world) then the DM is –1.
  • If Size is A (high gravity world) then the DM is –1.
  • If Atmosphere is not 5, 6 or 8 then the DM is –1.
  • If Atmosphere is 5, 6 or 8 then the DM is +1.

With either variation, the end result is that almost all systems will be populated (2d6-4 means 83.33% of at least population 1). The digit translates like so:












A tiny farmstead or a single family




A village





Tens of thousands


Small town


Hundreds of thousands


Average city





Tens of millions


Large city


Hundreds of millions





Present day Earth

10 (A)

Tens of billions


11 (B)

Hundreds of billions


Incredibly crowded world

12 (C)




The Slightly Modified Version

In essence, there’s nothing wrong with this roll – it fits the Traveller assumptions of a Earl Dumarest-style universe of countless inhabited but more or less isolated systems.

The assumptions aren’t quite what I’d like; I’d prefer highly-populated Garden worlds surrounded by tons of smaller border colonies.

With that in mind, I’d probably go with 2d6-4, and add (in addition to the “hard science” DMs):

  • +1 if the world has water (hydropgraphics 1+)
  • +1 if it is Temperate
  • -1 if it is frozen or boiling
  • -2 if it is searing
  • -2 if size is 11 or higher

This way the maximum positive DM is +3 (2d6-1), resulting in “hundreds of billions” of people, and habitable worlds. A garden world will always be inhabited though; the GM should probably omit population rolls for worlds he knows were never explored or add a “fudge factor”, a negative DM for “undeveloped subsectors”.

A searing super-earth with an unpleasant atmosphere is 2d6-9, so it will have at most “thousands” of people.

An Asteroid base with temperate “climate” will be at the default 2d6-4, the same as in the standard Traveller rules (the additional -2 is negated by the +2 for temperate climate).

Again, these numbers would have to be playtested, but I think they should work.