The different numerical values within each category (i.e., nuclear disarmament, nuclear non-proliferation and nuclear security) reflect each activity’s importance within that area, as determined through deliberation by the Research Committee of this project. However, the differences in the scoring arrangements within each of the three categories do not necessarily reflect a category’s relative significance in comparison with others, as it has been driven by the differing number of items surveyed. Thus, the value assigned to nuclear disarmament (maximum score of 101) does not mean that it is more important than nuclear non-proliferation (maximum score of 61) or nuclear security (maximum score of 41).

Regarding “the number of nuclear weapons” (in the nuclear disarmament section) and “the amount of fissile material usable for nuclear weapons” (in the nuclear security section), the assumption is that the more nuclear weapons or weapons-usable fissile material a country possesses, the greater the task of reducing them and ensuring their security. However, the ResearchCommittee recognizes that “numbers” or “amounts” are not the sole decisive factors. It is definitely true that other factors—such as implications of missile defense, chemical and biological weapons, conventional force imbalances and a psychological attachment to a minimum overt or covert nuclear weapon capability—would affect the issues and the process of nuclear disarmament, non-proliferation and nuclear security. However, they were not included in our criteria for evaluation because it was difficult to make objective scales of the significance of these factors. In addition, in view of the suggestions and comments made to the Hiroshima Report 2013, the Research Committee modified the criteria of the following items: current status of the roles and significance of nuclear weapons in national security strategies and policies; relying on extended nuclear deterrence; and nuclear testing. Since the Hiroshima Report 2014, these items have been negatively graded if applicable.

As there is no way to mathematically compare the different factors contained in the different areas of disarmament, non-proliferation and nuclear security, the evaluations should be taken as indicative of performances in general and not as an exact representation or precise assessment of different countries’ performances.

The Hiroshima Report 2020 basically maintains the same structure and items as previous years’ reports, while one item on the TPNW has been added since the Hiroshima Report 2018. Besides this, since the Hiroshima Report 2019, the Research Committee has added an evaluation item addressing whether the respective countries attended the Hiroshima or the Nagasaki Peace Memorial Ceremonies while attendance at the Hiroshima Peace Memorial Ceremony alone had been evaluated until the Hiroshima Report 2018. (the maximum score of three points in this item remain the same). Furthermore, since the Hiroshima Report 2020, increase of the number of possessed nuclear weapons in the past five years, and activities that are not covered by the existing evaluation items but contrary to nuclear disarmament and non- proliferation are negatively graded, respectively, if applicable.