Lost due to piracy would be a relatively piddling amount, since a significant portion of any of the silver convoys was only taken once (by the great Dutch admiral Piet Hein's fleet in 1628, during the Eighty Years' War). I'd be more interested in the weather stats.Are there any estimates of how much treasure was sent from the Conquistadors back to Europe that was lost due to sunken ships or piracy or other causes?
Don't know either of them offhand, though. Hein's action resulted in the capture of 11.5 million guilders' worth of loot, for whatever that's worth.