Often agricultural earnings cannot easily be quantified.是什么意思？

Often agricultural earnings cannot easily be quantified.

农业收入经常很难用数量来表示.

often

adv. 常常，经常，时常，再三；

例句
Genetic abnormalities are more often associated with faults in paternal DNA than in maternal DNA.
相对于母本DNA,基因畸变往往更多地与父本DNA上的缺陷相关。

agricultural

adj. 农业的，耕种的，农艺的，农学的；

例句
Many of the old agricultural collectives are now being turned into agribusiness corporations.
许多老式的农业合作群体现在正在转型为农业综合经营公司。

earnings

n. 收入，所得，工资，报酬，收益，利润；

例句
Despite a reduction in earnings there are compensations in moving to the north-east where the quality of life is excellent...
尽管钱会挣得少一点，搬到生活质量高的东北部去还是有很多好处的。

cannot

=can not，未可，不能，不可；

例句
...parents who feel they cannot cope or might abuse their children.
认为自己应付不来或可能会虐待孩子的父母

easily

adv. 容易地，很可能，迅速地，频繁地；

例句
The Centre is easily accessible to the general public...
该中心普通大众可随意进入。

be

v. 是，有，存在，做，成为，发生；aux. 用来表示某人或某物即主语本身，用来表示某人或某物属于某一群体或有某种性质；

例句
The older child should be able to prepare a simple meal...
那个年纪稍大的孩子应当会做一顿简单的饭菜。

quantified

v. 确定…的数量( quantify的过去式和过去分词 )；

例句
The final protein was quantified with Bradford assay.
Bradford法测定蛋白的得率.