Percentage followed by per mille
Examples
For example, 45% (read as "forty-five per cent") is equal to the fraction 45/100, the ratio 45:55 (or 45:100 when comparing to the total rather than the other portion), or 0.45. 
Percentages are often used to express a proportionate part of a total.
(Similarly, one can also express a number as a fraction of 1,000, using the term "per mille" or the symbol "‰".)Related units
Percentage point difference of 1 part in 100
Per mille (‰) 1 part in 1,000
Basis point (bp) difference of 1 part in 10,000
Permyriad (‱) 1 part in 10,000
Per cent mille (pcm) 1 part in 100,000
Grade (slope)
Centiturn