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Superstar
That MAY be a reason (or one of many) but if there are, say, 3 times as many international flights @ Terminal 1 one might expect to have 3 times as many CBSA agents etc etc. there too. As @allengeorge notes in his/her excellent post above, there are many interconnected reasons and far too many players!It could be because there is more international flights that go into terminal 1 then terminal 3.