15-9
2. The Shapley value approach is recommended. It is fairer than the incremental method
because it avoids considering one user as the primary user and allocating more of the common
costs to that user. It also avoids disputes about who is the primary user. It allocates costs in a
manner that is close to the costs allocated under the stand-alone method but takes a more
comprehensive view of the common cost allocation problem by considering primary and
incremental users that the stand-alone method ignores.
More generally, other criteria to guide common cost allocations include the following:
a. Cause and effect. It is not possible to trace individual causes (either Internet access or
phone services) to individual effects (uses by Evan or Brett). The $90 total package is
a bundled product.
b. Benefits received. There are various ways of operationalizing the benefits received:
(i) Monthly service charge for their prime interest––Internet access for Evan ($75),
and phone services for Brett ($25). This measure captures the services available to
each person.
(ii) Actual usage by each person. This would involve keeping a record of usage by each
person and then allocating the $90 on a percent usage time basis. This measure
captures the services actually used by each person, but it may prove burdensome,
and it would be subject to honest reporting by Evan and Brett.
c. Ability to pay. This criterion requires that Evan and Brett agree upon their relative
ability to pay.
d. Fairness or equity. This criterion is relatively nebulous. One approach would be to split
the $90 using the Shapely value or the stand-alone method.
15-24 (20 min.) Allocation of common costs.
Barbara Richardson, a self-employed consultant near Sacramento, received an invitation to visit a
prospective client in Baltimore. A few days later, she received an invitation to make a presentation
to a prospective client in Chicago. She decided to combine her visits, traveling from Sacramento
to Baltimore, Baltimore to Chicago, and Chicago to Sacramento.
Richardson received offers for her consulting services from both companies. Upon her return,
she decided to accept the engagement in Chicago. She is puzzled over how to allocate her travel
costs between the two clients. She has collected the following data for regular round-trip fares with
no stopovers: