Less clear, however, is whether or not
assortative mating is on the rise. Answering this question is hard, because the ratio of
educated men to educated women has
shifted over time. That university-educated men are now more likely to marry university-educated women may not show a change
in -. It may simply
reflect the increased number of women
with degrees.
单词注解
ratio:
a relationship between two amounts, represented by a pair of numbers showing how much bigger one amount is than the other 〔两个数量之间的〕比，比例，比率
the ratio of sth to sth 以……的比例
Men outnumber women here in the ratio of three to one
此地男子数量以三分之一超过女子
The ratio of nursing staff to doctors is 2:1.
护理人员与医生的比例为2比1.
翻译：
然而，是否门当户对这个趋势处于上升还不清楚。因为受教育男女比例一直在改变，所以回答这个问题是困难的。受过教育的男子可能会和受过教育的女子结婚，但在配偶偏好方面可能不会改变。这可能反应了有学历的女子的数量在上升。
语法：
1.Less clear, however, is whether or not assortative mating is on the rise.
这是个部分倒装句，however是个插入语。正常语序是Whether or not assortative mating is on the rise is less clear.
部分倒装的形式：(1)助动词，情态动词或be 动词放到了主语的前面。
(2)以否定词开头的句子要求部分倒装
Not until yesterday did little John change his mind.小约翰直到昨天才改变了主意。
(3)以否定副词开头并加状语放在句首的句子要求部分倒装。这些否定副词有barely, hardly, little, seldom, scarcely…… when, never, no sooner…… than, rarely, no more, not nearly, not only和only
Only in the country can you learn the “true English”.
你只有在这个国家里才能学习真正的英语
完全倒装:表+系+主.
2.That university-educated men are now more likely to marry university-educated women may not show a change in spousal preferences. It
may simply reflect the increased number of women with degrees.
在这个句子当中that引导的是主语从句.
That 的用法
a.它用来指已被提到的人或物；也可表对比,指两个中较远的那个.相当于形容词的用法，后加名词
What about that book you borrowed from me last month?
b.that 可引导定语从句(关系代词)，指代主句或主句中的某个名词，当在从句中充当宾语时可以省略。也可作关系连词，只有在定语从句中才是关系代词。
C.that可以引导主语从句，放于句首。适用于it作形式主语的句型，
That obama is the president of the USA is all known to us=It is all known to us that obama is the president of the USA.
众所周知，奥巴马是美国总统。
用于表示愿望或期盼，常用虚拟语气
That I could fly in the sky. 我要能在天上飞就好了。