When you say "Spending" do you mean how much is being currently purchased or Year's culmulative domains purchase? After all, someone could "buy" 100 domains but give 99 of them back within the grace period, ending up not having a high yearly amount. So which?
This is common during drop times as many people use the API for drop catching domains, particularly higher spending accounts who generally have priority over the API connections. The API connection is based on spending.