It is obvious in the graphic/table that the rate/number/amount of Y has undergone dramatic changes. It has gone up/grown/fallen/dropped considerably in recent years (as X varies). At the point of X1, Y reaches its peak value of …(多少). 
  
  
　　What is the reason for this change? Mainly there are … (多少) reasons behind the situation reflected in the graphic/table. First of all, …(第一个原因). More importantly, …(第二个原因). Most important of all, …(第三个原因). 
　　From the above discussions, we have enough reason to predict what will happen in the near future. The trend described in the graphic/table will continue for quite a long time (if necessary measures are not taken括号里的使用于那些不太好的变化趋势).