Velocity

I just wanted to enshrine these words of Kent Beck before they're lost in the aether. Read carefully:

Another purpose of measuring capacity is to improve throughput. If you plan for less than your capacity, you get less done than you could have. If you plan for more than your capacity, you get less done than you could have.

Having a plan with "enough" work in it less some slack to improve the probability of meeting commitments increases the amount of work that gets done compared to planning for too much or too little.