I think you're going into all this assuming IG is making their own sort of betting platform for the weekend. Reality is they hedge against the dark pool with st

I think you're going into all this assuming IG is making their own sort of betting platform for the weekend. Reality is they hedge against the dark pool with standard market orders - against other banks or large institutions who also have the need to hedge. Big banks typically still let you buy FX over the weekend, and if you have a good feed you can see the activity over the weekend - though the spreads are larger. This is also how the FX market opens with a weekend gap - because of the trades on the weekend, remember FX markets don't have opening auctions. The index products are just extensions of the FX market but on smaller more centralised dark pools. Its also heavily profitable to trade on the weekend because you can have your bids and asks very wide and simply make money off the spread. Its IGs job to aggregate them down and they make their spread revenue that way.