So when you're deep in focus, or trying to be, and there's an interruption or ad-hoc open-floor brainstorming meeting right next to you, you just blink once or twice and shift over to some easy-pickup task you already have waiting in the back of your brain? Add a zero to your rate.
If you can squirrel away a little bit of time here and there to make hard things easier, then you can eventually start breaking tasks down into chunks that fit better into a day of interruptions.
This has been the only way that I've found to consistently increase my productivity no matter how much I'm procrastinating or being distracted at the time.