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Assessment @ VIU Library: Overlap Analysis


Establishing the overlap (+open access +foreign language) % of a particular database

1. Download the title list of the database you're evaluating from the vendor and paste it into a spreadsheet in Excel.  Make note of how many titles are on the list.  Next download the title lists of the databases you'd like to compare the original list with and paste each list into a separate spreadsheet in the same document. Repeat for as many databases as desired. 

2. Many vendors pad their lists with open access titles.  If you'd to remove these, create another spreadsheet and paste in the titles.  A list of Directory of Open Access Journals (DOAJ) titles is available for download at


3. You'll need to set up a system for removing duplicates that are found when you're comparing one title list to another.  I recommend a $15 Excel plugin called Remove Duplicates from AbleBits.  If you'd like to compare columns without a plugin, here are the Excel directions on comparing data across columns.  Here's a visual example of what the Remove Duplicates plugin does:

4. Select the spreadsheet containing the title list of the database you're evaluating and run the Remove Duplicates plugin.  When asked what spreadsheet you'd like to compare it to, select another spreadsheet.  For example, if I'm evaluating Academic Search Premier, I click on that spreadsheet, run Remove Duplicates, and select the JSTOR spreadsheet.  This will compare the titles in JSTOR to ASP and remove the duplicates on the ASP sheet. 


5. Repeat step 4 until you've compared the title list of the database up for evaluation with all the other title lists.  You compare these one at a time.


6. You should be left with a title list that has a number of titles removed.  Once the duplicates have been removed, you may wish to scan the title list of the database up for evaluation and remove foreign language titles. 


7. Compare the number of titles left with the number of titles you began with.  Divide the number that's left into the original number and multiply by 100.  For example, if you began with 500 titles and only have 250 remaining after removing duplicates/OA/foreign titles, the calculation would look like this: 250/500 x 100 = 50%

Subject Guide

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KJ Reed
Assessment and Data Librarian
Vancouver Island University
900 Fifth Street
Nanaimo, BC
V9R 5S5

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