Determining the Distribution of Maintenance Categories: Survey versus Measurement

In 1978, Lientz, Swanson, and Tompkins ("LST") published the results of a survey on software maintenance. They found that 17.4% of maintenance effort was categorized as corrective in nature, 18.2% as adaptive, 60.3% as perfective, and 4.1% was categorized as other. We contrast this survey-based result with our empirical results from the analysis of data for the repeated maintenance of a commercial real-time product and two open-source products, the Linux kernel and GCC. For all three products and at both levels of granularity we considered, our observed distributions of maintenance categories were statistically very highly significantly different from LST. In particular, corrective maintenance was always more than twice the LST value.