in, the total number of ballots originally allotted to the polling place, and so on. Note that this vote count analysis is separate from his analysis of statistical anomalies in the PREP voting timeline. His September 7, 2006 paper (in English) discusses both of these analyses. Some, including Mochán in his article note that undervotes may result from citizens who decide not to cast their ballot; overvotes may result from poll workers failing to register a citizen in the log; and so on. According to Mochán (p. 14 in) others have speculated in the press that the majority of overvotes and undervotes come from so-called "contiguous polling places" and are the result of confusion on the part of the voters, who deposited their ballots in the wrong box (the explanation follows). Mochán neither confirms nor denies the provenance of the overvotes and undervotes, and only reports aggregated totals. The reason for this possible confusion is the following: the law places a hard limit of 750 voters per polling place (article 192.2 of the COFIPE). For districts with a high population density (particularly in cities), usually a single location will contain several polling places in order to split the voters among them (article 192.3.B). These polling places are usually assigned a single number; one is designated as the "basic" polling place, and the others are designated with a second number identifying them as "contiguous 1", "contiguous 2", etc. Each one has its own officials and ballot boxes. However, being in close proximity (often without any physical separation between them) it is not uncommon for voters to be confused as to which box corresponds to which polling place (this kind of error is mentioned several times in Mochán's article; see e.g. pp. 10 and 14 in). This confusion results in a ballot for one polling place being deposited in the ballot box corresponding to an officially different polling place, giving both an undervote for the correct polling place and an overvote for the incorrect one. According to the COFIPE (Federal Code of Electoral Institutions and Procedures), article 231 a ballot which is placed in the wrong box should be moved to the correct box if possible (as is the case, for example, if the presidential ballot is deposited in the senatorial ballot box), but should in any case be counted and reported. A single such vote would appear as both an undervote