## 3 Current Developments
### Contributor Analysis
#### 3.2.1 Participation Inequality  
Similarly to other open source-related or online community-based projects, VGI platforms experience a so-called \"participation inequality\". [PERSON] [123] describes this phenomenon with a 90-9-1 rule, representing the 90% of users who never contribute to the project and merely function as \"lurkers\", the 9% of contributors that add information on an irregular basis and the 1% of contributors that account for almost all the collected information of the project. This phenomenon has been identified for Wikipedia [108,124], as well as for OSM [71,125] in similar ways. The activity of the project's community has a major impact not only on the collection of new geographic data, but also on timeliness of existing datasets. In the context of UGC platforms, the widely used online encyclopedia, Wikipedia, had almost 20 million registered members at the beginning of October, 2013, of which, a total of 1.7 million members (9%) had edited at least one article, but only 125,000 members (0.7%) had performed an action to articles in September, 2013 [126]. It needs to be noted, however, that these numbers do not include changes made by unregistered, anonymous contributors. Similar patterns can be found in VGI projects, such as OSM. In 2008, about 10% of the 30,000 registered members actively contributed to OSM [127]. This positive trend continued in the following year (2009) for which a study had shown that, in total, about 33,400 (28%) of the 120,000 registered members edited data for the project [125]. In 2010, the number of registered members increased to 300,000, of which almost 5% (16,500) actively contributed to the project on a monthly basis and only 3.5% of all members (12,000) accounted for 98% of the data volume [21]. In a more recent study, it was shown that 38% of the 500,000 registered OSM members edited at least one object of the projects dataset in 2011 [71]. Figure 2 illustrates the growth of registered members and their corresponding activity over the past eight years. It also highlights the strong discrepancy between the number of registered members and the active contributors who created a changeset. Additionally, Figure 2 illustrates the significant difference between the number of \"one-time-only\" contributors [7] who created only one changeset and contributors who performed several edits in the OSM database. The conducted research by [PERSON] and [PERSON] [71] also analyzed the contributor activities by day of week and time of day. Almost all weekdays showed similar contribution patterns; only on Sundays did the project prove to have a slightly larger number of data edits, while the afternoon and evening hours were identified as time ranges with the highest activity in OSM for each day. Overall, the discussed results of the OSM project match similar patterns previously found in Wikipedia [128] or mobile phone communication behavior [129]. [PERSON] and [PERSON] [71] also identified different member groups in OSM based on the number of contributions the members made to the project and revealed that only around 5% of all members contributed in a significant way. Although the absolute number of registered members is still increasing, the relative number of active members has been decreasing in the past two years. In 2012, only around 3% of all registered members made a contribution each month; at the end of 2012, only 18,000 (1.8%) of the one million registered members actively contributed any data. This negative trend continued in 2013. As of October, 2013, the OSM project had almost 1.4 million registered members and the number of active contributors in that month was only around 22,000 (1.6%) [130]. The negative trend in the relative contribution share is mainly influenced by the high amount of newly registered members in 2013 (Figure 2). Based on these prior findings, a number of studies questioned the long-term motivation of the contributors of the project [7,21,118].