一个句子的比较问题，求教NN~

As a result of the continuing decline in the birth rate, fewer people will enter the labor force [in the 1980’s] than did [in the 1960’s and 1970’s]

看到这样一句话，说这里的did不可省。。。为什么啊？！我觉得可省啊！省略就是时间状语的比较，没啥不可以啊~~求教NN~~

这里关键是时态
你如果直接说"than in the 1960's"，就是这个意思：
fewer people will enter X in the 1980s than (will people) in the 1960's
Make sense? No!!!! Because "in the 1960's" is a past time indicator, you have to change the tense.
fewer people will enter X in the 1980s than did people in the 1960's.

如果我现在说：fewer people will enter X in the 2030's than in the 2020's. 这没问题，因为同样可以用将来时表示。
所以说一旦有tense shift, 或者单复数的变化，必须补出来。这其实是parallelism的要求。

这里关键是时态
你如果直接说"than in the 1960's"，就是这个意思：
fewer people will enter X in the 1980s than (will people) in the 1960's
Make sense? No!!!! Because "in the 1960's" is a past time indicator, you have to change the tense.
fewer people will enter X in the 1980s than did people in the 1960's.

如果我现在说：fewer people will enter X in the 2030's than in the 2020's. 这没问题，因为同样可以用将来时表示。
所以说一旦有tense shift, 或者单复数的变化，必须补出来。这其实是parallelism的要求。

最后那个than ever before, than 1000 years ago 这里没有时态的变化么？为什么不补出助动词？

我觉得还是babybearmm说的那个时态原因~~你看她解析的很透彻哈~时态对还是可以这样省略哒，关键是看ETS表达的是不是语义清晰就好了~~

比如：
Rice has protein of higher quality than wheta does.(主语比较，Rice 与wheat比）
意义：米有高质蛋白质，麦没有。
Rice has protein of higher quality than of lower quality(介宾比较，of higher 与 of lower比）
意义：米有高质蛋白质而非低质蛋白质
Rice has protein of higher quality than that in wheat(宾语比较，protein 与protein(that指代)比
Rice has protein of higher quality than sugur.（宾语比较，protein 与sugar比）
意义：米中的蛋白质比麦中蛋白质质量高
意义：米中的高质蛋白质比糖多。
Rice has protein of higher quality than usual/everbfore/1000 years ago/people expected(状语比较）
意义：米比通常/经往/多年前/人们预测/的蛋白质质量要高。

这个higher在quality前面，比较也可以有很多种，不一定就是quality与quality的比较对不对？~