Animation playback speed control in Unity?

In my game, I need the speed of enemies (but not anything else) to increase as the game progresses, and/or base on enemy type. To do this, I was planning on setting the animation playback speed in script, as they use randomly selected animated paths. However, looking at the Animation script reference, as well as the Animation interface guide, I can't seem to find any way to do this. Is this really not an option? Do I have to create new animations for every increment of speed? I hope I can adjust the playback speed as I like to play with things like enemy speed when finding the feel of a game. Also, don't most 3D games that use analog control for the speed of a walk/run also adjust the speed of the animation (along with blending between other animations)? 3D game basics like this are why I feel like I must be missing something. Thanks for your help!

Look in docs for AnimationState.speed