Hi!

This and previous night I did a testbed regarding money production, especially trade revenue and income formula from a single planet, as in DA I had biger problems with early money than I had in DL, and the developers also stated the revenue was nerfed. I wanted to know by how much. The base money-making formula was discovered by random50 some time ago and is:

  34.5 * sqrt(population_in_billions) * tax_rate * (1 + (sum from buildings on planet)) * (1 + (sum from racial bonuses) ) 

More about it you can find on Wiki.

To be short: after running DA game version 1.50.59 for about 3 hours and 4 game-years on a class-20 planet with zero economy bonus (0% in abilities, no resources mined, no econ or government tech researched, no econ buildings built) and permanent 29% tax I found that the formula is still valid. The only change is the first constant - instead of 34.5 I used 28.5 and got a very good match between predicted results and most of the obtained data.

Conclusion: planets in DA provide 21% less money than in DL.
Addition(Jun 2007): Jonathan Hoof has found the constant in DA 1.6 has changed again: it is now about 24, so tax revenue is decreased for another 19%.

Other findings
1) Accuracy of formula with low and high population.
- below 0.3B of population was the formula not acurate, but that's probably because of rounding float-number income to a displayed whole number.
- Above 24B I actually started LOSING income. It went from initiall 40BC down to 38, but that was probably because of low approval on my testbed planet. It lost with the last 1B pop (from ~23.5 to 24.5B) about 40% approval, and the planet was "held" in range 30%-38% approval for about a year and a half, before additional Virtual Reality Centers were built and approval increased to 64%. The population started to grow again, when approval increased above 40%, but I noticed the increase in income only after the approval went over 50%, and the pop went above 28B. When I ended testing it generated from 36B pop 43BC income.

2) Trade revenue
In is common knowledge that starting value of trade route also depends on amount of population on both planets. My research proved that, however the effect is small. The first trade route from the observed planet, when it was at ~11B to Sol with 12B pop was worth 3BC. The value of the 8th, when the planet was at 24B was 4BC. Killing 30B pop by destroying all farms decreased trade revenue of all 8 trade routes from 143BC to 122BC.
When I replaced some VRCs and factories on the observed planet with Market Centers, increasing income from 43BC to 65BC, the trade revenue didn't change, when compared with the simulation run without MCs.
Conclusion: population has only a small effect (~15%) on trade revenue. For best results better take the longest possible trade route, instead a route between two most populous planets.

3) Approval on the observed planet
Tax level was 29%, unchanged through the whole testbed. I had to tell that I have built on the observed planet alltogether 13 VRCs (6 to get planet just to 40% approval), the Secret Police Center (that seems doesn't work) and a Galactic Resort. I also had ALL morale "wonders" and 2 mined morale resources, each providing 24% boost to morale, the race had 35% initiall bonus, so at the end it had morale ability of 165. At the same time when the observed planet struggled for 40% approval, my planets with 16-18B pop (a farm on 100% bonus tile) and a single morale building (not even VRC) enjoyed a 100% approval, and planets without one and with 13B also the 100% approval.
Conclusion: if you've been dreaming about having a really big population: forget it! Not worth the hassle, not even close to be worth the expenses.

4) Having enough time while observing that planet I also tested Orbital Terraformer. It properly converts all tiles, and properly increases the PQ, also for planets that were colonized after it was built. So if you want to have those tiny PQ-1-2-3 planets as proper monster planets, postpone all terraforming until you build OT.

5) Game glitch
When I set up a planet as civilization capital, and then set another one, the first one it retained its base food of 12 until I reloaded the game.

I hope something of that stuff I wrote is useful.

BR, Iztok

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For those who like raw data, here's the table with pop and money it generates at tax 29% and without single econ bonus. BTW in some turns I missed writing down the amount of pop when the income changed, but have written the next one. Two columns are from tests with DA 1.5 and DA 1.6.

Tax	population in B
(BC)	DA 1.5	DA 1.6
2        0,1
3	0,2	0,204
4	0,26	0,344
5	0,43	0,542
6	0,6	0,816
7	0,71	1,142
8	1,16	
9	1,26	1,814
10	1,49	2,038
11	2	2,428
12	2,35	2,934
13	2,8	3,606
14	3,2	4,054
15	3,55	4,726
16	3,85	5,39
17	4,45	6
18	5,05	6,67
19	5,35	7,344
20	5,8	8,24
21	6,43	9,13
22	7,15	9,808
23	8	10,928
24	8,34	11,824
25	9,1	12,672
26	9,85	13,79
27	10,06	14,912
28	11,41	16,03
29	12,2	17,15
30	13,2	18,448
31	14,06	
32	15,11	
33	16,6	
34	17,1	
35	18,12	
36	18,89	
37	20,06	
38	21,48	
39	22,21	
40	24,5