Immortality and compound interest are a powerful combination. Wealth and power has always beget wealth and power, and immortality allowed a select few to take advantage of this process as never before. This was the birth of the hyperelite, those whose wealth represented a significant fraction of the global economy, and seemed to own a part of every business and political body.
The Fall shattered this system just as it did to everything else, yet the hyperelite were not destroyed. Many of the hyperelite were already on Luna or Mars, where they could live as they liked, removed from Earth's laws, traditions, and taxes. Those on Earth were able to evacuate as they pleased, buying spaceports and farcasting facilities if necessary. The only hyperelite who died on Earth were those who were simply too stubborn to consider leaving.
Earth and all its institutions were dead. The hyperelite lost less than most, but their position was threatened. They had, however, funded or owned much of the colonization projects of Luna and Mars, giving them easy access to power in those places. In the traumatized post-Fall atmosphere gaining influence was not difficult, although many hyperelite still shied away from positions of formal power. As the situation stabilized, a number of conversations occurred that would lead to the creation of the Convention.
The Convention is not a government, but a treaty, establishing an economic zone of free trade, expansive property rights, and strict intellectual property laws, as well as a system of courts to adjudicate on matters falling under the treaty. The Convention courts have the authority to overrule local governments that contradict the treaty, although that has not actually happened, as hyperelite backers
Hyperelite control over Convention members is strong, but obscured. Power is exercised mostly through ownership of great conglomerate companies, who in total own or have some part in every substantial piece of economic activity. Make no mistake, however, their political power is secondary but still substantial.
Notes: The Planetary Convention is an alternative to the Planetary Consortium, replacing the hypercorps with ancient hyperelite gerentocrats.