Change on Day

Historically the LSE has declined to provide guidance on net and/or percentage change values, merely advising that change values should be representative; this may have led to differing vendor conventions being applied over time.

Order Driven Instruments

However, Section 3.2.2 of the Recommended Display and Derived Guidelines now recommends that the "difference between the last order book trade price and the previous trading days' closing price for order driven markets" is made available, and this is the guidance being followed.

Ordinary trades are not included as they may be delivered out of sequence with automatically-executed trades, and moreover continue to be reported until after the end of continuous trading, which may cause confusion.

Quote Driven Instruments

For quote-driven instruments (where there is no order book), a slightly different logic is used, and the net and percent change values are calculated as the difference between the current mid-price (mid-point of best bid and offer) and the mid-close.