As I consider the different charts, models and diagrams most often used to explain the concept of technical debt, it occurs to me that they are missing an important dimension, which I will call ‘sensitivity.’ In short, does this item/problem/issue matter within the larger context of its (eco)system? This dimension was also missing from the static analysis tools I wrote and used earlier in my career, which severely impacted their usefulness, and therefore their usage.
In particular, I remember deploying FindBugs at Google , and the conclusion that the tool could not determine the impact of the defects it found because it had no context. Putting that context into economic terms, what is the price of an item, or perhaps the price of either fixing or ignoring it? We talk about costs and benefits, which to my mind are generally fixed quantities. But the price of a item is variable, and allows us to bring the powerful laws of supply and demand into the picture.
“What’s it worth to you?” I asked myself. When I was facing 100,000 build targets with missing direct dependencies while attempting to disallow transitive build dependencies , my price was very low. Once I had automatically fixed all the easy cases, my price rose as the goal got closer. I priced the final few, most difficult fixes very highly, as the value of all the earlier work depended on their timely completion. Once finished, the build system permanently enforced the desired property, essentially making the price infinite from then on. The debt in question had been paid off.
So, I am arguing that we use some analogy of ‘price’ as the measure of what matters in the larger context, and let the ‘market’ set that price for each TD item. Some items will be quite price sensitive, others quite insensitive, to extend the metaphor. This will bring the social aspects of economics into our models, and perhaps cube the quadrants by adding another orthogonal dimension.
 Nathaniel Ayewah, William Pugh, J. David Morgenthaler, John Penix, YuQian Zhou. Evaluating Static Analysis Defect Warnings on Production Software. Proc. 7th ACM SIGPLAN-SIGSOFT Workshop on Program Analysis for Software Tools and Engineering, ACM Press, New York, NY, USA (2007).
 J. David Morgenthaler, Misha Gridnev, Raluca Sauciuc, Sanjay Bhansali. Searching for Build Debt: Experiences Managing Technical Debt at Google. Proc. Third International Workshop on Managing Technical Debt, IEEE (2012).