eDiscovery Daily Blog

The Number of Pages (Documents) in Each Gigabyte Can Vary Widely: eDiscovery Throwback Thursdays

Here’s our latest blog post in our Throwback Thursdays series where we are revisiting some of the eDiscovery best practice posts we have covered over the years and discuss whether any of those recommended best practices have changed since we originally covered them.

This post was originally published on July 31, 2012 – when eDiscovery Daily wasn’t even two years old yet.  It’s “so old (how old is it?)”, it references a blog post from the now defunct Applied Discovery blog.  We’ve even done an updated look at this topic with more file types about four years later.  Oh, and (as we are more focused on documents than pages for most of the EDRM life cycle as it’s the metric by which we evaluate processing to review), so it’s the documents per GB that tends to be more considered these days.

So, why is this important?  Not only for estimation purposes for review, but also for considering processing throughput.  If you have two 40 GB (or so) PST container files and one file has twice the number of documents as the other, the one with more documents will take considerably longer to process. It’s getting to a point where the document per hour throughput is becoming more important than the GB per hour, as that can vary widely depending on the number of documents per GB.  Today, we’re seeing processing throughput speeds as high as 1 million documents per hour with solutions like (shameless plug warning!) our CloudNine Explore platform.  This is why Early Data Assessment tools have become more important as they can provide that document count quickly that lead to more accurate estimates.  Regardless, the exercise below illustrates just how widely the number of pages (or documents) can vary within a single GB.  Enjoy!

A long time ago, we talked about how the average number of pages in each gigabyte is approximately 50,000 to 75,000 pages and that each gigabyte effectively culled out can save $18,750 in review costs.  But, did you know just how widely the number of pages (or documents) per gigabyte can vary?  The “how many pages” question came up a lot back then and I’ve seen a variety of answers.  The aforementioned Applied Discovery blog post provided some perspective in 2012 based on the types of files contained within the gigabyte, as follows:

“For example, e-mail files typically average 100,099 pages per gigabyte, while Microsoft Word files typically average 64,782 pages per gigabyte. Text files, on average, consist of a whopping 677,963 pages per gigabyte. At the opposite end of the spectrum, the average gigabyte of images contains 15,477 pages; the average gigabyte of PowerPoint slides typically includes 17,552 pages.”

Of course, each GB of data is rarely just one type of file.  Many emails include attachments, which can be in any of a number of different file formats.  Collections of files from hard drives may include Word, Excel, PowerPoint, Adobe PDF and other file formats.  So, estimating page (or document) counts with any degree of precision is somewhat difficult.

In fact, the same exact content ported into different applications can be a different size in each file, due to the overhead required by each application.  To illustrate this, I decided to conduct a little (admittedly unscientific) study using our one-page blog post (also from July 2012) about the Apple/Samsung litigation (the first of many as it turned out, as that litigation dragged on for years).  I decided to put the content from that page into several different file formats to illustrate how much the size can vary, even when the content is essentially the same.  Here are the results:

  • Text File Format (TXT): Created by performing a “Save As” on the web page for the blog post to text – 10 KB;
  • HyperText Markup Language (HTML): Created by performing a “Save As” on the web page for the blog post to HTML – 36 KB, over 3.5 times larger than the text file;
  • Microsoft Excel 2010 Format (XLSX): Created by copying the contents of the blog post and pasting it into a blank Excel workbook – 128 KB, nearly 13 times larger than the text file;
  • Microsoft Word 2010 Format (DOCX): Created by copying the contents of the blog post and pasting it into a blank Word document – 162 KB, over 16 times larger than the text file;
  • Adobe PDF Format (PDF): Created by printing the blog post to PDF file using the CutePDF printer driver – 211 KB, over 21 times larger than the text file;
  • Microsoft Outlook 2010 Message Format (MSG): Created by copying the contents of the blog post and pasting it into a blank Outlook message, then sending that message to myself, then saving the message out to my hard drive – 221 KB, over 22 times larger than the text file.

The Outlook example back then was probably the least representative of a typical email – most emails don’t have several embedded graphics in them (with the exception of signature logos) – and most are typically much shorter than yesterday’s blog post (which also included the side text on the page as I copied that too).  Still, the example hopefully illustrates that a “page”, even with the same exact content, will be different sizes in different applications.  Data size will enable you to provide a “ballpark” estimate for processing and review at best, but, to provide a more definitive estimate, you need a document count today to get there.  Early data assessment has become key to better estimates of scope and time frame for delivery than ever before.

So, what do you think?  Was this example useful or highly flawed?  Or both?  Please share any comments you might have or if you’d like to know more about a particular topic.

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