The expansion and contraction of the journalistic field and American online citizen journalism, 2000–2012

•A new dataset with a near-population of citizen journalism web sites is introduced.•Between 2000 and 2012, the population of U.S. citizen journalism sites increased and declined.•Organizational population dynamics and technological change affected the population.•Political upheaval and disruptions in professional journalism offer weaker explanations. While previous research has considered patterns of homogeneity and heterogeneity in the journalistic field, existing literature has largely ignored the factors that contribute to the growth and contraction of the field. Using citizen journalism (CJ) as a case study, we examine how four forces – organizational population dynamics, technological innovations, exogenous political events, and endogenous disruptions elsewhere in the field – shaped the growth of CJ over time and, consequently, the journalistic field. Using a snowball sampling method, we collected a “near-population” of U.S.-based, English-language CJ sites (n=1829) to measure yearly density and rates of foundings and mortalities. The population of CJ sites increased through most of the period, foundings declined after a spike in 2005, and mortalities rose dramatically after 2010. The results provide evidence that organizational population and technological change affected the size of the population of CJ sites, while political upheaval and disruptions within professional journalism held less sway.