improve的名词形式是什么

　　An improvement in living standards could be years away.

　　生活水平的提高可能还要几年。

　　We expect to see further improvement over the coming year.

　　我们期望来年会有更进一步的改善。

　　CBS's ratings again showed huge improvement over the previous year.

　　哥伦比亚广播公司的收视率比过去的一年又有了大幅提高。