Spreads on London-traded US index ETFs - lower when USA open?

[EthicsGradient]

I have sometimes seen that a bid-offer spread can be larger overnight - which makes some sense, since the market makers are having to predict at what price a stock may open at. For ETFs traded in London, but whose tracked index is mainly or entirely American, it might also make sense that the spreads would be larger in the UK morning, when the underlying US stocks are not being actively traded (there are futures, of course, but they seem more volatile).

Does anyone know if there is any analysis of this?

[rhys]

I prefer to trade VUSA and IUSA because of their size and apparent narrow spreads of about 3p compared to smaller ETFs that track the S&P500, such as CSP1, SPXP, HSPX.

Some of the smaller ETFs also show wild swings when there's any news and at NYSE opening times.

[EthicsGradient]

For what it's worth, I checked on the spread of 2 US-index ETFs on the LSE - at the weekend, one was about 0.4%, another 0.15%. Both were about 0.15% all the way through London trading on Monday and Tuesday.