Productivity Decline in Directed System of Systems Software Development

The “Incremental Productivity Decline” (IDPD) factor represents the percentage of decline in software producibility from one increment to the next.
The decline is due to factors such as previous-increment breakage and usage feedback, increased integration and testing effort.
Another source of productivity decline is that maintenance of reused previous build software is not based on equivalent lines of software credited during the previous build, but on the full amount of reused software.
Build 1: 200 KSLOC new, 200K Reused@20% yields a
240 K ESLOC “count” for estimation models.
Build 2: there are 400 KSLOC of Build 1 to maintain and integrate
Such phenomena may cause the IDPD factor to be higher for some builds and lower for others