In both cases, every effort has been made to report purely domestic telegraphic activity, excluding foreign sent and received, as well as in-transit messages. However, in some cases (particularly in the pre-World War I period) the sources do not adequately distinguish between the several message categories, and occasional over-reporting may be expected. The latter is a serious reliability problem as regards certain Latin American countries during the latter years of the nineteenth century, when an unusually high proportion of telegrams fall into the foreign-sent and foreign-received categories.