Intergalactic trade is usually limited to within a star system, local group, or sector. It is rare, beyond military and entertainment goods, for trade to extend much beyond that or even on a UNG-wide basis.
The main reasons for this are logistics and consumption. As most of the colonies are small, most of their trade relies on small sized transport craft; craft that don't carry enough goods to justify the costs involved in beyond system or sector trade. In addition, local consumption either consumes all locally produced goods, or the goods themselves are uniquely suited to the locale of their production; in turn limiting their trade beyond the area.
The UNG has expended massive amounts of energies and efforts on expanding humanity to the stars in order to guarantee the survival of the species. With the cessation of cloning for the repopulation of the species in December, 2030, (though cloning for other purposes does continue by numerous parties, for good and otherwise,) a new industry sprang up virtually overnight: enticing second and third generation citizens from the larger colonies to the more distant ones. The result of this is a long term steady decline in the economies of the older and larger colonies. It is at the back of most people's minds that this trend will result in the eventual shift of power, and trade, from Earth and the Core of the UNG, to systems further out. The result could be akin to the collapse of Rome into a handful of larger territories, and numerous smaller ones.
Nevertheless, the short-term benefits of the migration of successive generations does have the immediate positive effect of economic stability in the older, larger worlds, a damper on inflation and a balancing of education levels between the older and the newer colonies; as the newer, smaller colonies cannot afford the educational institutions and resources of the older, larger ones.
A negative effect and a potential sign of the fracturing to come is the formation of protest groups, dissidents, and terrorist organizations actively working towards the dismantling of the UNG. The UNG has blindly and belligerently responded to this non-military crisis, and are actually assisting in the growth of these organizations.