Friday, June 25, 2010

Velocity targeting and velocity inflation

Continuing my mini-series on filling an iteration, velocity and all that I want to flag up a big big mistake: Velocity Targeting. Which leads to Velocity Inflation.

Velocity targeting happens when someone says: “We did 15 points last iteration, lets aim for 20 this iteration”. And when the team fails to meet 20 they say something like: “What happened? We didn’t meet our target?” - or perhaps they start assuming that because the target is 20 the can adjust the plans and message to stakeholders accordingly.

We can all fall into this trap: its called Hope. We hope for a better world. When it gets dangerous is when the person issuing such statements is in some position of authority, e.g. the word “manager” or “leader” is in their title, and they start issuing communications with the target as reality.

Given a few iterations the team will meet the target. However the means they use to meet the target may not be what is expected. And these may well create problems later on.

For example, the team might skip on testing or skip on refactoring. This results in a short term speed up which sacrifices long term maintainability and flexibility. You might actually choose to do this, with the agreement of the authority person, but this should be a conscious decision and you accept the long term slow down.

A more subtle but systematic problem is Velocity Inflation. In this case the team start giving larger estimates, so when work is done the amount done is greater, so velocity rises. The same amount of work is done but the point value is higher. (This can be a conscious or sub-conscious thing, I expect it is more often sub-conscious.)

In some ways this too is natural. Team members want to appear more successful, they want to achieve more, they want to please people - especially those who are in authority and set targets. But, and this is the real danger of Velocity Inflation, it undermines your ability to predict the future work capacity of the team because yesterday’s values can’t be compared to tomorrows.

Velocity inflation is just like financial inflation rational expectations and the Lucas critique need to be considered. It should come as no surprise that I’m going to quote Goodhart’s Law again:

  • “Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes.”

Targets are good when they help people to stretch and reach goals but in setting them you need to be aware of the side-effects. Simply to advocate targets is violation of Deming’s eleventh principle of management:

  • “11 a. Eliminate work standards (quotas) on the factory floor. Substitute leadership.
  • 11 b. Eliminate management by objective. Eliminate management by numbers, numerical goals. Substitute leadership.”

The solution is simple: don’t do it.

If you (quite naturally) want velocity to rise you have look elsewhere. That will be the subject of my next blog entry.

1 comment:

  1. very interesting post.

    i couldn't get an understanding of rational expectations from the wikipedia article, other readers may like to look here:


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