As architecture firms are business, most have staff that are NOT architects but probably only the largest of firms. This would include marketing, human resources, etc. However, over 80% of architecture firms are small (less than 5) and the architects on staff do all of the work.
One source of information is the following - most of the members of SDA are not architects, but rather those within the firm that assist in the areas previously mentioned.
Society of Design Administration
I hope this helps!