I have found some success, when playing countries with a small population base, to make the following treaties with everyone I can;
Free Flow of Labor
I do see an increase in immigration after a flurry of treaties.
I do this any time I ally someone.
All my production costs are below market levels, I'm only producing at 105% demand. I need more income, I've been in the game for four years with the same budget restrictions. Right now I've cut almost all military spending and put it toward research. I'm only surviving off selling petrol to my allies.
I believe here is what is avoiding your economy to grow, all the commodities that are sold to your population should be at max.
This will increase demand?