How Common Is Spellcasting?

The ability to cast spells is a rare inborne gift in Kordoth and Ekeria at large. Only 1 in 10,000 individuals are active Saints or members of the Arcane Conclave.  
Many speculate that the ability to cast spells is a hereditary gift given by Jai-Blynn himself.  Others think it is entirely random.  What is known for sure that those born without the gift do not acquire it later.  There are legends of unskilled peasants getting blessed by Jai-Blynn but the veracity of such stories is often doubted.