Dictionaries of English are based on literary output. The first dictionary of American English was published a little over 200 years ago. It was a slim volume compared to the behemoths now available. Companies that sell dictionaries have their staff comb through newspapers, magazines, and books to look for new words, new uses of old words, and so on.
Dictionaries grow with the increase in literary output.
Dictionaries of nonliterary languages, by contrast, are based on the collection of oral text and the extraction of dictionary entries from those texts. In two weeks, they produced 25,000 words of Kom containing 2,600 unique words. Next year, we plan on building a dictionary from that corpus of work using a computer program that presents each unique word to a native speaker and that then asks for information about how the word is used. With a corpus of text as the basis of the project, every entry will automatically have one or more contextual exemplars. They had 150 volunteers walk around for two weeks with tape recorders tied to their waists.