Difference between 割合 vs 率

Question

割合 and 率 both mean ratio, rate, and percentage. What is the difference?

Answer 1

Neither means percentage. Percentage is one hundred times ratio or rate. The Japanese word for it is 百分率. Likewise, permillion is one million times ratio or rate. The Japanese word for it is 百万分率.

My impression is that 割合 and ratio are the general terms for a quantity divided by another quantity (usually but not always of the same dimension). 率 and rate are especially for cases where its lowness or highness is connected to its preferred amount in an ideal situation. For example, 率 or rate is used for 誤差~ or error ~ because the ideal case would be zero. It can be also used for 正解~ or correctness ~ because the ideal situation will be one. It is also used in 転送~ or bit ~ because the larger the better.

Answer 2

these two words literally share the similar meanings of ratio,rate. translation of the the explaination from the yahoo 知惠袋 website

割合 normally is used to refer to the proportion of sth,the relationship of one thing to another in size, amount, etc.

eg: 1. The proportion of men to women in the college has changed dramatically over the years. 近年学校の男女の割合を大きく変化しています。

 2. Limestone and clay in the proportion 2: 1.  
石灰石と粘土の割合は２対１also :
石灰石と粘土の比率は２対１

率 is often used after a sort of noun in order to express the percent of ...;for instance percentage "百分率", percent of pass "合格率", percent of attendance "出勤率" etc. and as mentioned above, when use with "比" as"比率", 比率shall substitute "割合".