This paper revises and updates the Campi-Nuvolari index of intellectual property protection for plant varieties. The new index provides yearly scores for the period 1961-2018 for 104 countries, which have legislation on plant variety protection in force. The new evidence highlights the ongoing shift towards more similar and stronger systems of intellectual property rights (IPRs) worldwide, regardless of individual characteristics of countries. The signing of the TRIPS and trade agreements with TRIPS-Plus provisions are major drivers of this process. In addition, certain characteristics of countries such as the regulatory environment, the level of human capital, the importance of agricultural production, and openness to trade, are also significant determinants of the evolution of IPRs systems. We conclude by discussing other possible applications of the data.