本文提出九类指标，用以分析选择螺旋首轮的传播行为和效应；本研究以城市品牌为选择因素，以京沪津渝港北 澳七城市为选项，以今日头条 2015-2017 年间 27 个月中 75971 条贴文为数据，来展示这些指标的运用。本文提出了传 播螺旋中的单项选择与累积选择的区别，前者包括发布量、读每发和转每读，后者包括发布量、点读量和转发量。本 文还提出了选择度、贡献率等指标，用以测量、比较和解读发布、点读和转发的行为。本项研究发现，螺旋中的选择 度直接影响信息分布；发布的选择度最强，点读次之，转发最次；因此，以首轮结尾的转发量分布为影响对象，发布 选择的影响最大，约贡献 66%； 点读者选择的影响次之，约贡献 28%； 转发选择的影响最小，约贡献 6%。这意味着， 传统媒体环境下发布群体垄断“议程设置”的传播生态可能已不复存在。取而代之的，是网络媒体环境下，发布、点 读、转发三个群体“协调议程”的传播生态。当然，在特定平台（今日头条）、时间（2015-2017）、选因（城市名） 和选项（七城市）等给定条件下，发布者仍然可起很大作用或主导作用（66%）。但主导弱于垄断，且两者背后的机 制大相径庭：过去，占人口极少数的发布群体因为垄断发布平台（媒体）而独掌议程设置；今天，人数剧烈扩大的发 布、点读或转发群体因为对内容的较高度选择而主导“议程协调”，或因为对内容的较低度选择而参与议程协调。 

This study recommends nine statistical indicators as tools for analyzing release, read, and relay behaviors in initial rounds of selective spirals ((IRoSS) of online communication. With city brand (city name) as the selecting factor, seven Chinese cities as the selections, and 75971 postings crawled in 27 months between 2015 and 2017 from www.toutiao.com as example data, we illustrated the calculation, application, interpretation of the proposed indicators for theory building or practical decision making. The study distinguishes per-act selections, i.e., release, read per release, and relay per read, from cumulative selections, i.e., release, read, relay, and relay per release. We combined features of correlation coefficient r and r 2 to produce directional r2 . We also developed indicators to quantify selectivity and contribution. The results show that agenda setting by senders through traditional media might be giving way to agenda negotiation between releasers, readers, and relayers through online communication. Releasers may dominate the negation, as in our data releasers contributed 66% of the content distribution at the conclusion of the initial round, while the readers and relayers contributed the remaining 34%. Unlike traditional senders who set the agenda by monopolizing the channels of mass communication, the online releasers negotiated the agenda with the receivers and relayers and exerted larger influence by being more selective than the other two role groups.