## 3 Results and Discussion  
We first assessed the development of Chinese archival work in six areas including the number of institutions, full-time employees, collection, opening and utilization of archives, the floor space of archives, and digital archives in the past four years, as shown in Figure 1.  
The number of institutions peaked in 2019 and 2020. The number of practitioners dropped significantly between 2018 and 2019. It may be the result of the institutional reform in 2018, in which only the national and provincial archive management agencies are retained, and the prefecture-level agencies have been canceled. Generally, the collection and utilization of archives have increased slightly over time. In the past four years, China went through poverty alleviation, the Winter Olympic Games, and the COVID-19 pandemic; a large number of archives has been produced during these large events and emergencies. At the same time, the floor space of archives has grown steadily and substantially every year. Moreover, the number of digital archives has stalled after a significant increase in 2019.  
Next, we calculated the overall scores to evaluate the performance across the years (Figure 2). In general, the development of Chinese archival work has been improving yearly, implying that the field has been paid more and more attention, the government's investment has increased, and the management system has become more scientific. We found that the score in 2021 is significantly higher than in other years, which may be related to the newly revised archives law on 1 January 2021. The law aims to promote the archive's governance, utilization, and security system, encourage the high-quality development of the field, and contribute to the modernization of the governance system and capacity. It provides a strong legal guarantee for the sustainable and high-quality development of the archival work. An interesting phenomenon is that we did not observe a significant impact of COVID-19. This indicates that the archival work is necessary for people's lives, and even though the epidemic has caused various restrictions and inconveniences, the development of the field has not been hindered.  
We analyzed the gaps in different years under the 25 indicators (Figure 3). We found some conclusions that were consistent with those in Figure 1, such as significant differences in the number of employees across years (corresponding to the substantial decline in 2018-2019). In addition, we obtained some new conclusions, for example: (1) The number of archive institutions and government information open access sites are relatively stable. The opening of archives has always been a difficult problem in archival work, so it is unlikely to make significant progress in a short period. (2) Affected by the COVID-19 pandemic, the number of archives and materials used, the number of users, and the number of exhibitions all show downward trends. (3) The number of people who need to use archives is relatively stable, and is not affected by the COVID-19 pandemic. This indicates that more people turned to digital archives.  
Figure 1: Development trend under different primary indexes. A, B, C, D, E, and F represent the number of institutions, full-time employees, collection, opening and utilization of archives, the floor space of archives, and digital archives certified by the competent archives department at or above the provincial level, respectively.  
We further analyzed the robustness of the model (Figure 4). We found that by removing any indicator, the impact on the total score should be less than four and, in most cases, less than two. Therefore, we believe that the results obtained by replacing the indicators in a limited range should all conform to the trend in Figure 2.