RE: Gregorio9 Jun 2020 00:40
TomE
FYI ref UT’s
SETSmm is an electronic, order driven, trading service with market makers. It is typically for slightly smaller less liquid stocks - the market makers provide liquidity. This is also an anonymous limit order book (except for Market Makers whose identity is disclosed) with opening and closing auctions.
In these markets, the trading day is as follows: 07:15 Market Opens 07:50 Start of opening auction 08:00 Opening auction ends and uncrossing algorithm runs to determine opening price, and automatic electronic order matching commences. For SETSmm the Mandatory Quote Period (MAP) commences - during this time Market Makers must provide firm 2 way prices 16:30 Automatic electronic order matching ceases and the Mandatory Quote Period ends. The closing auction starts. 16.35 Closing auction ends and uncrossing algorithm runs to determine closing price 17:15 Market Closes (Up until 17:15 market is open for trade reporting purposes)
On SETS and SETSmm nothing happens between the end of the closing auction and the start of the following day's opening auction. Obviously any number of factors (news/announcements/relationship of buyers to sellers etc) between the market close and the market open can, and do, impact the opening price.
The various market data providers should use the closing auction price as the closing price of the stock, but in reality the last reported trade is used.