(8)ESMA should refer to historical data indicating shifts in liquidity to determine both whether the class of derivatives or subset thereof is sufficiently liquid to trade only on venues and whether it is only sufficiently liquid in transactions below a certain size. The thresholds for these assessments may vary between classes of derivatives or subsets thereof where the characteristics and the notional size of the classes or subsets vary. In its assessment of spreads, ESMA should have regard to both the average size and the availability of spreads, balancing the consideration that a lack of or wide spreads indicate insufficient liquidity against the possibility that spreads may become narrower through increased transparency and the availability of the financial instruments if the trading obligation is introduced.