when you look at the size on the 5 bid prices and the 5 ask prices,it can be decieving,the old addage ,market always trades to size,is mostly not always true,when the big money wants to buy they throw up a lot of size offers hoping to keep the price low while they are buying and pull them 1 price at a time as the mrket moves up and vice versa,so if today you saw there were a lot more offers than bids and the market went up,that is why.