I've asked the same question about Level 2 in the past. For example, GALE normally has anywhere from 10% to 20% of its daily volume fall in between the listed Bid/Ask numbers. From what I have ascertained one needs access to Level 3 for complete Bid/Ask data which is restricted to NASD member firms that function as registered market makers. Retail traders with Level 2 see a lot of the Bid/Ask data but certainly not all. The big boys need their edge which is L3. If someone can educate us more on this topic please respond!
Concerning Wednesday's GALE trading there were 1,295,801 shares(42.2%) traded on the Ask, 1,255,329 shares(40.9%) traded on the Bid & 520,525 shares(16.9%) traded in between.