How to apportion a copyright in joint work by co-authors

As a matter of case law, the US courts would apportion the share of the copyright equally among co-authors, after a finding of co-authorship. The federal Copyright Act 1976 was the first legislative effort to statutorily provide for the doctrine of co-authorship in the US jurisprudence. However the 1976 Act neither clarifies the nature of co-authorship or how to apportion the shares, nor does legislative literature help. Courts are left with the task of clarification. Section 2 draws out two possible rationales behind the apportionment rule (the Equal Division Rule) and explores the difficulties. Section 3 proposes two alternatives (the Proportionate Rule) to the current apportionment rule based on the Default Theory analysis. For both works comprising quantifiable inseparable contributions and works comprising quantifiable interdependent contributions, the Penalty Default Theory favors the Proportionate Rule over the Equal Division Rule. Section 4 explores the interaction between the theories for co-authorship and the proposed alternative Proportionate Rule, and concludes that if the apportionment rule were instead devised to avoid the over-rewarding issue, as is the proposed Proportionate Rule, the courts would better conform to the statute and stick to a uniform test for co-authorship. Section 5 summarizes.