OK, found this: http://en.wikipedia.org/wiki/Data_compression_ratio

Which includes this section on "Usage of the term": "There is some confusion about the term 'compression ratio', particularly outside academia and commerce. In particular, some authors use the term 'compression ratio' to mean 'space savings', even though the latter is not a ratio; and others use the term 'compression ratio' to mean its inverse, even though that equates higher compression ratio with lower compression."

So, my bad, however in my practical workplace experience the above (in italics) has been the case, hence the confusion.