Horace,
IMHO
Bid/Ask volume on a DOM ladder IS NOT THE MARKET.
A market exists only when a trader crosses the Spread. It matters not how many Bids or Offers are positioned on either side of the Spread. What has to happen, is for a new seller prepared to sell below the spread or for a new buyer to pay higher than the spread.
The relative depth on either side can induce new trades to cross the spread, and in most liquid markets includes bids and offers which have been placed in the depth, only to try and influence general perception of strength or weakness.
If you think about it, sellers are always the controllers of market price.
eg. if last price traded was $10.00
where the next lowest holder prepared to sell his parcel is at $15, what happens?... nothing happens.
if a buyer appears at $12.00 and still no sellers below $15.. nothing happens.
Nothing happening continues until someone is prepared to cross the spread, either a new buyers steps up to pay the $15 ask or a new seller is prepared to accept the bid.
Why I say sellers control the market, if last sale was $10 and no bids exist above $5, the price does not automatically drop. Last price remains at $10.
Price heads to the lowest price where sellers exist. When all sellers are exhausted at a particular level, price can not fall further. Usually this creates a buying rush once bidders realise there is no chance to fill their orders at any lower level.
When price has been rising and suddenly there are no more buyers prepared to cross the spread, price will only drop if new sellers enter the market by crossing the spread to sell lower.