For all approaches, the most frequent error either consists in the insertion (Tesseract) or the deletion of whitespaces (all others) leading to merged or splitted words. This represents a common problem with historical prints, as the inter word distances vary heavily. The error distribution varies considerably for the different engines. For example, in the case of ABBYY the three most frequent errors make up to less than 5% of all errors, whereas OCRopus (close to 9%) and Calamari (over 15%) show a considerably more top-heavy distribution.