David Anderson has been presenting his thoughts on using the number of card pulls (Pull Transactions) as a metric for measuring the health and liquidity of a Kanban process. He starts the conversation here – http://agilemanagement.net/index.php/Blog/thoughts_on_the_value_of_liquidity_as_metric/
Our software has always charted the number of empty positions and queued positions over time which is a close proxy to this measurement and found the sum of Empty and Queued each time period a reliable indicator for forecasting where the stress points are in the Kanban board process. We decided that this liquidity chart might add an easier dimension for people to understand the impact of changes when they are experimenting with our simulation software. So we added the chart.
We are still refining the way it looks and going to add trend lines to make it easier to discern the running average, and we are also building a set of examples that show how it adds value. Remember -this is the ONLY chart where higher is BETTER. All of our other measure are lower is better – causing us some stress internally!