可是。。。。。正文P57，在“主语比较”1中：
“主语若相同，可省，但助动词不能省。如：
As a result of the continuing decline in the birth rate, [fewer people] will enter the labor force [in the 1980’s] than (few people省略)did [in the 1960’s and 1970’s], a twenty-year period during which people born after the war swelled the ranks of workers. ”
如果按照第一条所说的，岂不是did也可以省了，只留下介词短语in the 1960’s and 1970’s？？？
比如：Tom, who is 38 now, was 10 centimeters taller in his twenties than in his childhood. 因为两个比较对象都是过去情形，谓语动词都是一般过去式的谓语动词，所以【主谓】在第二次出现时，因为是和前者的完全重复就可以都省。
但是像P57 [fewer people] will enter the labor force [in the 1980’s] than (few people省略)did [in the 1960’s and 1970’s]
