Think about this: you're living on a world that is facing imminent destruction. Your government has located a new, uninhabited planet and is planning to migrate your people to it. They're planning to send people there in a series of ships, with each ship arriving around seven years after the previous ship.
Which ship would you go to the new planet on? Would you be a real pioneer on the first ship, raising the first building on the untamed world? Does the prospect of tagging along with the second group sound more up your alley? Or maybe you'd rather go with a later ship?