Why a boring FOMC statement led to lively market moves
There was one change in the statement
Aside from changing the dates, the FOMC statement was a virtual carbon copy of the prior one. The lone change was to say that business fixed investment had moderated from its strong pace earlier this year. The statement previously said it was strong.
So why the market moves?
Some of the move was simply flows that were queued up before the decision and were waiting to see if there were any surprises. There was clearly an imbalance toward USD buying in that.
At the same time, there was some worry or speculation the Fed would cool its language to tee-up a pause in Q1 2019. They didn't do that and on net, that's hawkish.
Nothing's changed for December and it's still very likely there will be a hike (the market is still priced around 80%, which is low in my opinion).