I thought it would be fun to share parts of, and expound on, classic traveller that we liked. One of my favorite adventures was trillion credit squadron (TCS).

So from p. 31

B = Cr500 x GM x P

Where B = annual naval budget.
GM = government modifier
P = population

The government modifiers are

 type     0    1    2    3    4    5    8    9    a    b    c    d
 peace  .50  .80 1.00  .90  .85  .95 1.10 1.15 1.20 1.10 1.20  .75
 war   1.50 1.40 1.50 1.20 1.45 1.40 1.20 1.20 1.50 1.20 1.50 1.50

I used to play a fair amount of TCS inspired traveller and I always thought the wealth of a planet should figure in too. If a planet is listed as rich more naval tax would be paid per capita and the reverse for a poor nation.

Rich could a 2X modifier to the formula. poor 0.5X.
Also in war ‘in extermis’ the GM should be even higher on a temporary
basis. The united states spent 37 of GDP at the height of WWII.

TCS had a chart to account for TL disparity for buying offworld items. Using this one could assume the TL9 for the near future for the world, for some nations at least which with no starport would modify .40 thus for the united states;

285mil pop X .85 X 500 X .4 = 48450 MCr

One could have a TCS hook that right now the groom lake area of Nevada is in fact to onworld end of a secret space development program.