i broke my own rule again, i foolishly bought macquarie group...

i broke my own rule again, i foolishly bought macquarie group today thinking i got a bargain for $185, it was $240 a few months ago, it closed on the days low of $174 and it will probably go lower as the DOW futures are way down again, should have just bought IVV, tell me this
the SP500 in the US last night closed down 4.87% right, yet IVV here on asx only closed down like 2.9%, didnt even come close to trading down 4.87%, why was IVV not down as much as the SP500 its supposed to track?