[en] The World Energy Council's definition of energy sustainability is based on three core dimensions: Energy Security, Energy Equity, and Environmental Sustainability of Energy Systems. Balancing these three goals constitutes a 'Trilemma' and balanced systems enable prosperity and competitiveness of individual countries. The World Energy Trilemma Index presents a comparative ranking of 128 countries' energy systems. It provides an assessment of a country's energy system performance, reflecting balance and robustness in the three Trilemma dimensions. To provide greater insight, we have evolved the methodology for the 2019 Trilemma and, for the first time, introduced visualisation of historical trends to enable the Trilemma performance of individual countries to be tracked back two decades to 2000. The new time-series analysis provides insights into a country's historical trends, challenges and opportunities for improvements in meeting energy goals now and in the future. The Index demonstrates the impact of varying policy pathways countries have taken in each of the dimensions over the past 20 years. Looking at these trends can inform a dialogue on national energy policy to promote coherence and integration to enable better calibrated energy systems in the context of the global energy transition challenge. Ten countries achieve the top AAA balance grade in the 2019 World Energy Trilemma Index, representing top quartile performance in every dimension. Since 2000, no countries have consistently improved in each dimension every year; instead most show historical trends with a variety of peaks and troughs in a general upward direction. Overall Trilemma performance for 119 countries over the 20-year period has improved, with only 9 countries seeing their overall performance declining. The rate of improvement in overall Trilemma performance also increases as the transition progresses and encourages countries to improve their energy policies. The overall top three countries across all three Trilemma dimensions are Switzerland, Sweden and Denmark. For the Energy Security dimension, the top performing countries in 2019 are Sweden, Denmark, and Finland. The top of the Energy Equity dimension traditionally ranks well-endowed or well-connected countries and geographically concentrated populations with access to abundant and affordable energy: Luxembourg, Bahrain and Qatar are the top performers in 2019. The leaders of the 2019 ranking for the Environmental Sustainability of Energy Systems are countries making steady gains on the pathway to decarbonization and pollution control, in the context of sustainable economic growth. The top performers in this dimension are also the overall Trilemma leaders - Switzerland, Denmark and Sweden. Across the different regions of the world, pathways through the transition are different, and leading countries in each region represent this diversity. The top 10 2019 Trilemma ranking is dominated by European countries, with Switzerland as the top performer in Europe both due to robust baseline systems and coherent policies improving upon these. Uruguay ranks highest of all Latin American and Caribbean countries, with high scores in the Security and Sustainability dimensions. In the Middle East and Gulf region, Israel ranks highest due to its performance in Sustainability compared to the regional average. New Zealand, with a placing in the global top 10, heads up the Asia-Pacific region with an AAA grade. Mauritius is ahead of other countries in Africa, balancing both Equity and Sustainability performance. Canada represents the best overall performance in the North American region due to strong Energy Security and a commitment to balanced and integrated energy policy