英语句子语法问题，为什么这一个句子里有两个独立句子？

Question

It reported a net loss of $6billion for fiscal 2016， the 10th straight year its expenses have exceeded revenue

Answer 1

It reported a net loss of $6billion for fiscal 2016， the 10th straight year its expenses have exceeded revenue.

前面是一个简单句，后面的含定语从句the 10th straight year its expenses have exceeded revenue.可看作fiscal 2016 的同位语。

追问

为什么后面的定语从句省略掉了引导词呢

Answer 2

个人理解如下：后面的这句话是来对fiscal 2016进行说明解释的，有两种形式来实现这个目的，一是用破折号（dash），二是用从句，所以这句话个人觉得中间的punctuation最好用破折号（这样好理解些），或者改为2016 which will be the 10th straight.....。
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