This question was asked in a mailing list:
We’ve had various view-points on this over the last few months. Is there “official” ruling on the percentage level of concentration [of magic] for normal people in any of the various Homelands?
Greg Stafford answers:
I have always contended that most people do not concentrate. Most people are extremely practical and perform whatever makes their survival easier, so they go to their regular services, make offerings and sing songs to Mr. Berry Bush and Old Man Acorn Grove, sacrifice when needed to Sister Water, The Guy in the Pool, wave their spell sticks over the butter pot to make that special cheese, pay the gal with the Healing Charms to get rid of the flux, eat the “color shrooms” when they need to find their cattle, go without food and water for three days when they want to find the pigs lost in the woods, chant over the birds found dead in the woods, bake special bread and leave it out for the things that used to come out of the woods, lay aside a portion of the ale for the ghosts of those who died near their creek, toss salt over their shoulder for good luck, cross their fingers and knock on wood, offer their own blood when the baby is sick, and so on and on and on, and never ever care a whit about Otherworlds, types of beings, type of worship or the types of magic.
Gloranthan people know there are several Otherworlds, but someone who has read the HeroQuest book knows more about the metaphysics that most Gloranthans do. They do not know and they do not care unless it will help to feed the kids and keep the fire burning in the winter. Concentration? That is what we do when we are trying to figure out how to make three pairs of boots out of one hide. Devotion? That is what I feel for my wife. It is an unfortunate fact that an unusual or rare thing (concentration, devotion) takes up a lot of space in the rules, therefore giving the impression that it is as important as the actually important things.
Most Sartarites are initiates because that is their custom, and most Pelorians are not, because that is their custom. Concentration is rare, less than 30%, because it really restricts survival opportunities. Devotion is rare, because it really restricts lots of opportunities.
But most important, YGWV (Your Glorantha Will Vary). It is a game, designed for you to enjoy and to have fun with. There is no “one way” to do it.