The ruling Communist party's policy allowing all couples to have two children came into force in 2016, leading to a 1.3m increase in births that year compared with 2015.

译文：执政的共产党允许所有夫妇生育两个孩子的政策在2016年生效，导致该年出生人数比2015年增加130万人。

句子语法结构分析如下

主语：The ruling Communist party's policy

后置定语：allowing all couples to have two children

谓语：came into force 

时间状语：in 2016

结果状语：leading to a 1.3m increase in births that year compared with 2015.

1. 请问本句中最后部份，that year是什么成份？是特指这一年还是代表某种从句？

解答：指代前面提到过的2016.名词短语that year作时间状语,不是从句

2. 还有compared with 2015是什么成份？

解答：compared with 过去分词作比较状语