DataSheet1_Predicting the Potential Applicability to Other Technical Fields Through the Linkage Between Backward and Forward Citations.docx

This article is a modest attempt to shed some light on the question of linkages between backward and forward citations in technical fields posed by Trajtenberg et al. (1997). They found interesting similarities and high correlations between equivalent measures looking forward and backward. They also implied the linkage between distant backward and distant forward citations. There are several questions to be posed in applying their insights to Japanese patent applications, however, due to the differences in the patent classification system and the subject of citation, i.e., citations by the applicant or examiner, between the US and Japan. In addition, and most importantly, the possibility that subsequent classifications may match, even if the first classification is different, is unavoidable with existing measurement methods of technical distance. In order to investigate these research questions, the author proposes a new measurement method for the technological proximity between examiner’s citations and their originating patents using IPC-based patent classifications. Using such a proposed method, the author created two hypotheses and tested them for about 14,000 examined patent applications filed in 2008 with the JPO. As a result of testing Hypothesis I, the author confirmed that Trajtenberg et al.’s insights can be applied to Japanese patent applications using citations by the examiners and IPC-based patent classifications. In other words, it was confirmed that patent applications citing backward citations categorized in a technical field distant from the invention are more likely to be cited by forward citations categorized in a technical field distant from the invention. As a result of the verification of Hypothesis Ⅱ, it was further confirmed in some technical fields that the backward citations categorized in a technical field distant from the invention are more likely to be in the same technical field as the forward citations categorized in a technical field distant from the invention. The author believes that these verified results indicate the possibilities of using backward citations as a starting point from which we can find patent applications for inventions at an early stage with potential applicability to other technical fields.

本文尝试性地厘清特拉滕贝格（Trajtenberg）等人（1997年）提出的技术领域内回溯引用与正向引用之间的关联问题。该研究团队发现，用于衡量正向与回溯引用的等效指标之间存在显著相似性与高度相关性，同时也暗示了技术领域相距较远的回溯引用与正向引用之间存在关联。然而，由于美日两国在专利分类体系、引用主体（即申请人引用与审查员引用）方面存在差异，将其研究结论应用于日本专利申请时仍存在若干待探讨的问题。此外，且最为关键的是，在现有技术距离测算方法下，即便初始专利分类不同，后续分类仍可能出现匹配的情况，这一局限无法规避。为解答上述研究问题，本文作者提出了一种基于国际专利分类号（International Patent Classification, IPC）的测算方法，用以衡量审查员引用文献与其所源自的源专利之间的技术邻近性。借助该方法，作者针对日本特许厅（Japan Patent Office, JPO）2008年受理的约1.4万件已审查专利申请开展了两项假设检验。针对假设一的检验结果显示，特拉滕贝格等人的研究结论可通过审查员引用文献及基于IPC的专利分类体系应用于日本专利申请场景。换言之，本文证实：若某专利申请引用的回溯文献所属技术领域与本发明所属领域相距较远，则该专利申请更易被所属技术领域与本发明相距较远的正向引用文献所引用。针对假设二的验证结果则进一步表明，在部分技术领域中，与本发明所属领域相距较远的回溯引用文献，更易与所属领域同样相距较远的正向引用文献属于同一技术领域。作者认为，上述验证结果表明，回溯引用文献可作为切入点，帮助研究者在早期阶段发掘具备跨技术领域应用潜力的发明相关专利申请。