In arm's-length combat, however, you should avoid the ground if at all possible. It is common to hear that "90% of all fights end up on the ground." This "statistic" comes from a study performed by the Los Angeles Police Department in 1997 (read more here), and is not at all accurate. While it is true that being trained in ground combat techniques can help minimize injury when you find yourself on the ground, you should not prefer this scenario. I know some martial arts instructors who will teach their students to take an opponent to the ground and then join him* there. I would strongly advise against this. Putting an assailant on the ground is a great idea, but you should keep your feet if you can -- this makes it easier to escape or to capitalize on your opponent's disadvantaged position. In addition, your assailant may have friends nearby, and voluntarily "going to the ground" puts you at their mercy. By all means, learn to fight on the ground, but use those skills only as a last resort.