RSS is the XML-based format for the syndication of web contents, and users aggregate RSS feeds with RSS feed aggregators. In order to effectively aggregate RSS feeds, an RSS aggregation policy is necessary. In this paper, we first propose an aggregation policy to minimize the number of postings being missed within an aggregation. Second, we analyze and compare our aggregation policy with existing aggregation policies. Our analysis reveals that our aggregation policy can reduce approximately 23% of the aggregation missing in comparison with the other aggregation policies while it increases only 6% of the aggregation delay.