Why is Market Share so important?

Why are there so many Share trades registered after the market closes at 16:30?

• If you look at the Trades information for most major shares (eg. any ftse100) then there are usually a good 10+ trades logged AFTER 16:30, which is normal market closing time. These are often quite large volumes/value trades eg. today 10th May, share Wolseley (WOS). According to Digital Look from 16:32 to 16:50, there were 12 share trades registered. The total value of these was around £20million. The prices for each trade varies widely, so I'm guessing they were actually transacted at various times during the day (or even previous days??) Presumably, if these trades are registered after 16:30, then the volume that is quoted for each trade is NOT included in the ongoing volume quotde during the day? So my questions are - what exactly are these trades and who is doing them. And more importantly, I thought the "market" was supposed to be transparent to all? So who "knows" about these trades prior to them being registered late in the day, and is there a way to see them earlier?

• Answer:

  Market is as transparent as it can be...and it will maybe get more so that way in the future. After Market hours trading typically is institutional traders (mutual funds, etc)...and market makers correcting trades. Additionally volume is created based on after the market reported earnings and global economic factors. -- its just that the standard operating hours are closed. These volumes need to be reported on the exchanges...but they're not recorded during the market hours as to not create trade imbalances and to the fact that the volumes are huge..because its typically bigger fish trading amongst themselves (a mutual fund manager calls another one and they exchange/negotiate a price in advance -- and then book the trade apres market hours).