It is obvious in the graphic/table that therate/number/amount of Y has undergone dramaticchanges. It has gone up/grown/fallen/droppedconsiderably in recent years (as X varies). At thepoint of X1, Y reaches its peak value of …(多少).
What is the reason for this change? Mainly thereare … (多少) reasons behind the situation reflected inthe graphic/table. First of all, …(第一个原因). Moreimportantly, …(第二个原因). Most important of all, …(第三个原因).