Is this really a KPI? It is really only measurable, not directly improvable. In addition, what does &quot;improving&quot; it mean? Is low good or bad? If we had a highly functional system and were growing 1000% then this number goes way up. Is that bad? This number, IMO, communicates very little between a CTO and CEO.<p>In additon, this number has no intrinsic value component. What is the value of being able to migrate to another system? Who cares? Rewrite for what? Does code rot? Are there bad spots like an apple? Does recreating the apple keep bad spots from being created next time?<p>There are only 4 states for a rewrite value judgement:<p>1. App is small and provides little business value..so who cares.<p>2. App is big, but low values so what&#x27;s it matter.<p>3. App is huge and high value so better be very very careful.<p>4. App is small and high value, so why?<p>Your ratios restate that and provide no additional information in the only state that matters which is number 3.