Percentage of total coins isn't the correct comparison, it's the percentage of total volume. We're on a pretty high volume day right now and the 24hr volume is at 150k. Some days it's a fraction of that, there have been multiple < 20k days recently. Depending on the day the mined coins are a significant percentage of the total being exchanged (not that all mined coins would be exchanged, but it's a fairly high number otherwise most people wouldn't have any BTC unless they mined it).
Regarding price, percentage of volume is the important metric. It is not relevant that ~12M bitcoins exist, if only, say, 1% of these are for sale on exchanges. Only coins for sale on exchanges help stabilize the price.
