factor in：include something as a relevant element when making a decision
factor (something) in，意思是“将......考虑进去”= “take something into account” “take something into consideration”
When housing and other living costs are factored in, a monthly salary of ￥15,000 in Beijing and Shanghai does not seem that handsome.
Once you factor in the specific circumstances, you will appreciate how heroic the pilot's action was. （注意当 factor something in 中的'something'较长时，我们可以把它放到后面，变成 factor in something。） (今天晨读也提到了）
【10-18】Students who are considered underachievers are actually overachievers once their socioeconomic statuses are factored in.
overachiever: to do better than expected or try too hard to be successful in study or work
1) Experienced writers will always factor in their writing purpose and the audience.
2) Moral quantity should be factored in weighing/judging/measuring the overall ability of the students.
I should factor in the mental illness of my roommate and always think of why she behaves differently.
