It is really quite probable that Kyonin is the richest, most peaceful, happiest country in the world, per capita. Those last two words are, admittedly, doing a great deal of work; the elven birthrate is 'do we have to?', and the elven death rate is More Than None, and there are not so many as there once were, for Kyonin, once the greatest of their realms, is now merely the last. Nonetheless the joy and safety and wealth of Kyonin remain.
Why and how is Kyonin the richest? Why, because elves are immortal; to a first glance, elves do not have 'unskilled labor'. By the time a human craftsman has spent forty years learning a skill, his mind is slowing and his muscles are starting to go, and so he must pass some of his work to unskilled others, and by the time he has spent a century, he is dead. Elves do not have that difficulty. By the time an elf has spent six hundred years mastering a skill and has felt the weakening in his muscles, he can afford to put one hundred years of the profits aside to pay for a Cyclical Reincarnation, and so elves can reach heights of craftsmanship of which humans can only dream.
Why is Kyonin the most peaceful? Why, because elves are, to a first approximation, mostly Good. Nearly fifty percent of the elves (who read as anything) read as Chaotic Good to Detect Alignment, and another thirty percent read as the other Good alignments. Per capita, there are fewer than a sixth as many Evil elves as mortals (referring only to the elves of Kyonin, and leaving the hateful Drow aside, as the elves of Kyonin prefer to), and few of those reach the same depths of Evil as, say, a typical person born in Cheliax. With so much Good, they need little Law to cope; an elf can simply trust that most other Elves mean well, and handshake deals are made that a human would either balk at or demand sworn oaths and Detect Alignment and Zone of Truth spells, eating up the gains from trade with expensive verification methods. The few children can simply play in the streets, with no worries about harm, doors can be left unlocked, favors can be given and met with favors and all these feed into Point One.
(Someone from outside Kyonin, who is, perhaps, used to thinking in terms of equilibria might ask, how is this stable? Won't individual evildoers prosper in this thieves' paradise, and - even if elves want so few children that they are a dying race - others copy them and learn from their methods? Why, no - elves are immortal. A reputation as dishonest will follow you for centuries, and very few people in prisoners-dilemma situations want to defect on the first move of a three-thousand-plus-unknown-turns iterated game. A smart evil elf isn't evil, and a dumb evil elf can be exiled before they reach their second century.)
Why is Kyonin the happiest? See points one and two, honestly, they mostly cover it.