Real-world software systems contain substantial
amounts of cloned code. While the negative impact of
cloning on software maintenance has been shown in
principle, we currently cannot quantify it in terms of
increased maintenance costs. However, as long as its
economic impact cannot be quantified, control of cloning is
probable to be neglected in practice. This paper presents
an analytical cost model to estimate the maintenance effort
increase caused by code cloning. The cost model can be
used to assess the economic impact of cloning in a system
and to evaluate investments in clone management tool
support. To show its applicability, we report on a case
study that instantiates the cost model for 11 industrial
software systems.