data在某一个时间段固定不变：fixed in time
在一系列的时间段中转变：changes over time
持续变化的data在不同情况下:
增加：increase / raise / rise / go up ...
减少：decrease / grow down / drop / fall ...
波动：fluctuate / rebound / undulate / wave ...
稳定：remain stable / stabilize / level off ...
最常用的两种表达法：
动词 + 副词形式(Verb+Adverb form)
形容词 + 名词形式(Adjective+Noun form)
1. Verb+Adverb form
The number of XXX
+increase/jump/rise/decrease/drop/fall/fluctuate...
+insignificantly/significantly/slightly/suddenly/rapidly/dram
