如何用英语表示增长了0.3％?求详解并说下为什么.

increased by 0.3%表示增长了0.3%,
比如说,The per unit area yield of ginned cotton has increased by 0.3% over last year.（皮棉的单位面积产量比去年增加了0.3%.）
increase to
增长到…
如,Both drinking and smoking among young people are increasing to an alarming extent.（在青年人中饮酒、吸烟的现象已发展到惊人的程度.）

increased by 0.3%
by 表示增长了
to 表示增长到

increased by 表示增长了多少多少
例句：But in the short term, individual Americans buying cover for next year have already seen their premiums ······ increase by ······an average of around 20%.
而从短期来看，每一个购...