Percent or per cent

How should I choose between writing "percent" and "per cent"?

For example:

He sold 42 percent of his stock in the company.

or

He sold 42 per cent of his stock in the company.

Are there different styles which I can choose from as long as I'm consistent, or is one of these correct/incorrect in some specific situations?

Solution 1:

Both percent and per cent are acceptable. The ODO's AmE entry carries the following note:

Origin: mid 16th century: from per + cent, perhaps an abbreviation of pseudo-Latin per centum

Both spellings, percent and per cent, are acceptable, but consistency should be maintained. Percent is more common in US usage; per cent is more common in British usage.

The AmE vs. BrE difference can be confirmed (to an extent) by these two ngrams. Also, as you've stated, it's important to be consistent with whichever choice you make.

Solution 2:

Just to add an Australian perspective to this one... The Commonwealth Government Style Guide (Sixth Ed.) says:

The spaced form, per cent, is recommended: it is the one most commonly used in Australia; it is given priority by both the Macquarie and Australian Oxford dictionaries.

It does go on to add ( in support of the earlier answer):

However, percent is the dominant form in the United States and is being increasingly used in the United Kingdom

Solution 3:

There is potential for confusion through using "per cent" where % is intended, as, if a cent were worth more, in a formulation (which would admittedly, in this example, at least, probably have the actual meaning readily clarified by context) such as "I got forty per cent.", where the argument could be made "I got forty/¢ (i.e., 40 [somethings] per penny/cent)", as opposed to "I got 40%". The two meanings are clearly as different as between 40th (fortieth) and 1/40 (fortieth), but in no circumstance can "percent" be confused for /¢ instead of %, whereas "per cent" could. Theoretically.

Solution 4:

Nowadays 'percent' is more preferable than 'per cent', considering the many different currencies with their units of measurements. E.g 'per cent' may be perceived as an actual unit against a cent.