Stairway to Harmonization: The Future of the Inverse Ratio Rule After Skidmore

Patrick Reed is a J.D. Candidate, 2021 at NYU School of Law.

On March 9, 2020 in Skidmore v. Led Zeppelin, 2020 WL 1128808, the U.S. Court of Appeals for the Ninth Circuit upheld a district court decision finding that Led Zeppelin’s famous 1971 rock anthem, “Stairway to Heaven,” was not “substantially similar” to Spirit’s 1968 song, “Taurus,” and thus did not infringe on Spirit’s copyright. Since neither party disputed that Spirit owned the copyright to the “Taurus” composition, the appeal centered on the degree of similarity between both songs’ opening notes, which Spirit alleged contained a similar chord sequence and bass line. In affirming that there was no substantial similarity between the two songs, the Ninth Circuit took the opportunity to overrule the long-standing “inverse ratio” rule as a method for evaluating similarity by assessing the likeness between two works with the defendant artist’s access to the original work.

The Ninth Circuit had been noted for its longstanding use of the “inverse ratio rule.” Under the landmark 1991 Supreme Court decision, Feist Publications, Inc. v. Rural Telephone Services Company, a plaintiff may prevail on the copyright infringement claim only if they demonstrate both “(1) ownership of a valid copyright, and (2) copying of constituent elements of the work that are original.” In demonstrating the second prong of the copyright infringement claim, the Ninth Circuit requires that a plaintiff must show both (1) copying (“access and similarities must exist, but they need not be extensive nor involve protected elements of the plaintiff’s work”) and (2) unlawful appropriation (“the similarities between the two works must be “substantial” and they must involve protected elements of the plaintiff’s work”). To find unlawful appropriation, the plaintiff must satisfy both an “extrinsic test” (which “compares the objective similarities of specific expressive elements in the two works”) and an “intrinsic test” (testing “for similarity of expression from the standpoint of the ordinary reasonable observer, with no expert assistance”). Although explicitly rejected in the Second, Fifth, Seventh, and Eleventh Circuit courts, the Ninth Circuit allowed satisfaction of the extrinsic and intrinsic tests with the “inverse ratio rule.”

The Ninth Circuit first articulated the “inverse ratio rule” in Sid & Marty Krofft Television Prods. v. McDonalds Corp. In Sid & Marty Krofft, the Ninth Circuit held that since a “very high degree of similarity is required in order to dispense with proof of access” to find copying, then the logical inverse would posit that “where proof of access is offered, the required degree of similarity may be somewhat less than would be necessary in the absence of such proof.” In its 2000 decision Three Boys Music v. Michael Bolton, the Ninth Circuit more clearly articulated the inverse-ratio rule as “requiring a lesser showing of substantial similarity if there is a strong showing of access.”

The inverse ratio rule was met with immediate criticism. Critics argued that lesser-known musicians could bring weak copyright claims against famous defendants whose works had extremely high similarity to plaintiffs’ works, but who had very little access to plaintiffs’ works. On the opposite side, famous plaintiffs could argue that high access of their works justifies their infringement claim against lesser-known artists, whose works were otherwise entirely dissimilar. In both cases, the inverse ratio test allowed plaintiffs to avoid the Ninth Circuit’s stringent extrinsic and intrinsic tests for copyright infringement, which require both technical similarity recognized by music experts and impressionistic similarity by laypersons.

Although independent creation is an affirmative defense to copyright infringement, critics of the inverse ratio rule contend that the thresholds for access are lower as artists become more interconnected. As music streaming and hosting services have provided new platforms for lesser-known, independent artists, established artists run the risk of inadvertently composing songs that mirror what they had once heard on streaming platforms. Independent creation is an affirmative defense to copyright infringement, but an unclear threshold for legally sufficient “access” to trigger copyright infringement has made the inverse ratio rule an overpowering tool for copyright plaintiffs.

Critics have also noted the Ninth Circuit’s inconsistent application of the inverse ratio rule. Within the Sid & Marty Krofft decision, the Ninth Circuit appears to back away from broad application of the inverse ratio rule in noting how “it is impossible to quantify this standard.” Without guidance on how to balance access with similarity, the Ninth Circuit and its constituent district court ended up ignoring the rule. In Aliotti v. Dakin, the Ninth Circuit complained that the inverse ratio rule was “confus[ing] and even conceal[ing]” how substantial similarity played a role in the copyright analysis. In Skidmore itself, the court acknowledges that after Aliotti, the court “returned to the inverse ratio rule and, in a series of cases throughout the 1990s and early 2000s, applied it in confusing ways.” This confusion may stem from the inverse ratio rule’s conflating the “copying” and “unauthorized appropriation” elements for a copyright infringement claim. While the copying element looks at the allegedly infringing artist’s access to the original work, the unauthorized appropriation element looks at substantial similarity between the two works. The inverse-ratio rule muddies copyright infringement analysis and distracts from the original purpose of copyright infringement doctrine: preventing unauthorized exploitation of copyrighted works.

The Ninth Circuit’s explicit refusal and candid language of the inverse ratio rule in Skidmore signals a clear divorce between the copying and unauthorized access analysis. While access can still provide circumstantial evidence that the defendant actually copying the work, the Skidmore court recognizes that “access, however, in no way can prove substantial similarity.”  To find substantial similarity, the Skidmore court urged a reorientation towards the extrinsic and intrinsic tests that have become a cornerstone of Ninth Circuit copyright doctrine. Time will tell how artists will respond to the Ninth Circuit dramatic overruling of long-standing precedent, but legal scholars are already praising greater harmonization in copyright doctrine between the federal circuits.