Single word for "continuous improvement"

I'm looking for a noun that represents the idea of ongoing improvement. It needs to be directional, alluding to movement and progress. "Improvement" by itself isn't right because it suggests that something is broken and needs fixing. All help is appreciated.

Solution 1:

There's a word that has been borrowed from Japanese to describe continuous process improvement in manufacturing, "kaizen". I'm posting this as an answer based on the suggestion in the comments, and the fact that it is in several of the English dictionaries that I checked.

• a business philosophy or system that is based on making positive changes on a regular basis, as to improve productivity.

Ngram: kaizen.

(from dictionary.reference.com)