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HathiTrust+Bookworm (HT+BW) visualizes word trends in 4.8 million public domain works held by the HathiTrust. It is currently being developed under a two-year NEH Implementation Grant, but it can already be tried at

The world's great research libraries have, over time, carefully assembled a rich body of metadata pertaining to the books in their collections. Since the HTRC has access to volume-level metadata as well as volume-level content, we have constructed a Bookworm of the HathiTrust public domain corpus. We felt that setting up Bookworm with a HathiTrust corpus would provides scholarly researchers with the means of exploring trends.


This tool enables scholars to discover new textual use patterns across the entire corpus. In the future, we plan to ingest the entire HathiTrust corpus and continue to identify appropriate metadata to use for the faceted browsing. This tool will be particularly useful to scholars interested in books that are still under copyright - which is the case for most books published after 1923. Although these books will not be available for reading or downloading online, working with individual words and phrases and tracking their occurrences through time will be useful to academic researchers, especially historians, sociologists and literary scholars.

John Unsworth has noted that a fundamental goal of the humanities is appreciation: "by paying attention to an object of interest, we can explore it, find new dimensions within it, notice things about it that have never been noticed before, and increase its value" (2004). Shifting from traditional close reading to a large-scale view of text presents a profound discomfort for humanities scholars, due to the difficulty in retaining the same sensitivity to what is actually contained in the works being studied. HTRC-Bookworm will function as a link between quantitative analysis (distant reading) and close reading. According to Frederick Gibbs and Daniel Cohen, "any robust digital research methodology must allow the scholar to move easily between distant and close reading, between the bird's eye view and the ground level of the texts themselves" (2011). This is what HTRC-Bookworm intends to accomplish (within the limitations of applicable copyright laws.)

Current limitations and future improvements

  • The current instantiation (the alpha version) of the HTRC-Bookworm is set up to work with 4.8 million out-of-copyright volumes from the HathiTrust corpus. Overall the HathiTrust has more than 14,000,000 volumes in all their corpus.

  • As a demonstration we have selected some metadata for use with this smaller corpus, but we are open to feedback on improvements to this metadata.

  • Our plan is to ingest the larger HathiTrust corpus and to allow facets to be selected based on HTRC worksets.

Overview of Tool

The search field

Currently, HT+BW supports one-word (unigram) entries as search terms, entered via the search field:


Facet fields

The facet fields display the options for faceted search. Initially, clicking "All texts" will pop up a menu that displays the possible facet fields. After a selection is made, you can modify it again by clicking on that label. Initially, on clicking "All" or inside this box, a popup menu displays a scrolling list of values that can be selected for the given facet. Multiple values for a given facet field can be chosen by clicking inside this box. Multiple values in a facet field constitute a logical OR for search purposes. So, for instance, in the example below, the  search will be for "Genre:Biography OR Poetry". Different facet fields are in an implicit AND relationship with each other. In the figure below,  three facet fields have been specified. The search criteria specified in this example translate into "(Class:unknown) AND (Genre: Biography OR Poetry) AND (Format: Book)."


"Settings" button

Clicking on the "settings" button, shown by the "gear" icon which is next to the "i" icon, will pop up a menu for changing display options to specify "Time", "Metric", "Case" and "Smoothing".

  • Time: Time range can be adjusted by dragging the "Time" slider for begin point and end point to the left and right as necessary.
  • Metric: This selection allows you to choose how the numerical values are counted. Depending on what option you choose, the label of the y-axis of the graph is changed accordingly, and the chart values adjusted. The four options available are as follows:
    •  "% of words" shows how frequently the unigram or bigram is used relative to all other tokens in the corpus, for the given year shown. This lets you see how often a word is used relative to the size of the corpus, without having to worry about things like whether there are more books in 1850 than 1900.
    •  "% of texts" gives the number of texts that use your search terms at least once as a proportion of the total number of texts published that year. Unlike "% of words," it will not be skewed by a single book that uses a word hundreds of times; however, it may be impacted by changing sizes.
    • "word count"  plots the actual count of the searched word as the y-value for the plot.

    • "text count" plots a count as the y-value for the plot that is computed in the following way: only those volumes in which the searched word actually occurs are counted for creating the plot. So, each such volume registers as only a single count. (The word "text" is being used interchangeably with the word "volume".)

  • Case:  
    • Selecting the "Insensitive" button will ignore the distinction between lowercase and uppercase characters when counting words 
    • Selecting "Sensitive" will maintain the distinction between lowercase and uppercase.

  • Smoothing:  "Smoothing" is a means to create a moving average over the data and to identify overall trends by removing jagged and discontinuous data points. To see the raw data points, set smoothing to 0. To average one point on each side of a data point, set smoothing to 1, which counts previous one, current one, and next one and divides that sum by 3. A smoothing setting of 5 means that 11 values will be averaged, 5 values on each side of the data point. The leftmost and rightmost data points will average fewer values. So with a smoothing of 1, only 2 data points will be averaged. Often trends become more apparent when data is viewed as a moving average. A smoothing of 1 means that the data shown for 1950 averages the raw count for 1950 plus 1 year on either side. Smoothing windows are weighted: the year shown is weighted the most heavily, and the weights decrease in each direction until the smoothing span is reached. A smoothing of 0 means no smoothing at all: just raw data. After setting "smoothing" to 5 years, the same graph looks more continuous and less jagged, as shown below.

Accessing individual volumes in the HathiTrust Digital Library from HT+Bookworm

You can click on any point in the plot to see a listing of the volumes by decreasing order of contribution to the plot at that particular year. Each volume title is a hyperlink, clicking on which will take you to the corresponding volume in the HathiTrust Digital Library.


Michel, Jean-Baptiste, Shen, Y. K., Aiden, A. P., Veres, A., Gray, M. K., Pickett, J. P., ... & Aiden, E. L. "Quantitative analysis of culture using millions of digitized books." Science331.6014 (2011): pp. 176-182.

Unsworth, John. “Forms of Attention: Digital Humanities Beyond Representation," delivered at "The Face of Text: Computer-Assisted Text Analysis in the Humanities,The Third Conference of the Canadian Symposium on Text Analysis (CaSTA), McMaster University, November 19-21, 2004.

Gibbs, Frederick W., and Daniel J. Cohen. "A Conversation with data: prospecting Victorian words and ideas." Victorian Studies, Vol. 54, No. 1 (2011): pp. 69-77.

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