We have included one union catalogue, ESTC, in this study. It is evident that ESTC is not complete in the sense that it would include all the recorded documents in different libraries. Going through some of the records of larger repositories, such as the National Library of Scotland quickly reveals that their collections includes at least dozens of documents not yet recorded in the cumulative ESTC. This, however, is not a problem for our analysis because we are mainly focused on general trends that do not require all the possible records in order to be reliable (QUOTE LL  [Löytyskö tähän joku data science reference? - voi olla hankalaa, tää on yleistä tilastoymmärrystä - mutta katsotaan varmaan jotain löytyy - mites esim se Culturomics-Science paperi]). One particularly interesting feature of ESTC is the high proportion of duodecimo documents (Fig. 1). At the end of eighteenth century, duodecimo in ESTC reaches the same level as the fast-dropping folio. Compared to the proportions of gatherings in the HPBD, for example, this is a highly noticeable feature. In the SNB, folio is at the same level as duodecimo, but the share of the total volume is much lower than in the ESTC. This can be largely explained by differences in the printing costs and market responses for the demand for cheaper reads [CITE: \cite{stclair2007} **]. If we analyse different cities based on book format proportions, we realise that it was especially places in North America, such as Boston MA (Supplementary Fig. 1) and Philadelphia Pa, Ireland and Scotland, Dublin, Edinburgh and specifically Glasgow where duodecimo format has the highest share of the print area. Interestingly, in London, folio seems to keep it's relatively high market share even in the latter part of the eighteenth century. Also in the traditional University towns of Oxford and Cambridge duodecimo does not rise to the top-2 formats in the later eighteenth century, which is noteworthy in the Anglo-American context.