It may take some research and inquiry to find the national cost-benefit compilation of agricultural products from 1998 to 200 1. Here are some suggested methods: 1. China Academy of Agricultural Sciences: This institution is one of the leaders of agricultural research in China, and may provide some agricultural economy and agricultural product cost benefits. You can try the search function above, or contact their department and ask if you can provide relevant information. 2. National Bureau of Statistics: The National Bureau of Statistics is the main provider of statistical data in China, and their websites may have agricultural-related data. You can try to find the relevant ones through the search function on their website or by looking at the statistics published by them. 3. Ministry of Agriculture: The Ministry of Agriculture is the main institution for formulating agricultural policies in China, and it can collect and compile some agricultural economic data and information. You can try to ask whether you can provide relevant information through the Ministry of Agriculture or contact their departments. 4. Academic research institutions: Some universities and research institutions may conduct agricultural economic research and publish relevant reports and papers. You can try to query some academic databases, such as CNKI and Wanfang. , and search for articles or reports related to 1998 to 200 1 cost and benefit of agricultural products. 5. Libraries and archives: Some large libraries and archives may collect and preserve some historical agricultural materials. You can try to contact some large libraries or local archives to find out whether they are relevant or can provide relevant help. Please note that specific data is not easy to obtain, and it will take some time and research to find the most accurate and comprehensive.