A census is a type of debt document used in the middle ages. See a translation of this Catalan Wiki Article , which explains it very well. 'Censuses' were very common in Catalonia in the middles ages, as well as in Italy. They help explain the birth of capitalism later in Early Modern era. The 'census' is a paper that documents payments to be made, yearly, in exchange for an investment received. 'Censuses' were created and redeemed. They were similar to present day mortgages, also public debt instruments (bonds), and other long-term investment documents, depending on the features agreed in the document.