Given also are the time periods, which set the long-term problem in years.这是一个完全倒装句。主句的主语带了一个非限制性定语从句，使得主语长，谓语短，头重脚轻，违反了英语句子尾重的原则。通过表语前者，主谓完全倒装，就避免了头重脚轻。不倒装的句子本来是这样的：

The time periods, which set the long-term problem in years，are also given。

这个句子主句的谓语不是被动语态，是系表结构，过去分词given是表语。

表语前置是完全倒装句的条件之一。如下句：

The house is in the south of the city.

In the south of the city is the house where Luxun used to live.