While observing time and sales data I've noticed large prints often outside of the NBBO, normally with market center D. These prints sometimes follow a flurry of activity or after a large iceberg is filled. What do these prints represent? Any feedback would be appreciated.
Ive always assumed that these are broker to broker negotiated block trades. These trades are not going though the open market, but they have to print them on the tape within a certain amount of time after the transaction. Also if it happens after a flurry of activity it could just be a clean up print finishing up an order.
These trades are also through pipeline and other such venues which arent available to most traders. These are known as dark pools and they now account for about 10% of daily market volume. The sec is concerned about this fragmentation of liquidity but probably won't do anything about it because these venues are pretty much used by institutions and hedge funds.