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The ED Therapist

Dear ED Therapist:

We are currently gathering about 30 GB of documents for electronic discovery and are trying to ascertain how long it is going to take us to review them. Obviously, every hour spent reviewing is going to increase our total bill, so we want to minimize review times. What can we do?

Speedy Gonzalez – Needles, CA

Dear Speedy,

You have hit upon a key factor in electronic discovery that many individuals overlook and that is the time and cost involved with actually reviewing documents. In nearly every matter the most expensive portion is not going to be electronic processing or keyword searching or even document conversion but rather document review. How long document review takes will depend on a variety of factors, including the type of information being reviewed, the review format, the review platform and the capabilities of the reviewer. Unfortunately, there is no silver bullet when it comes to estimating review time and cost. I will cover some of the factors involved and discuss various options, but I will also leave you with a quick-and-dirty, back-of-the-napkin ball park estimate method.

Review Speed
The question of “How fast can one review documents in any other review environment?” can or will be used as a way to demonstrate efficiency and reducing cost of attorney fees. Here are a few points to consider and a guideline for talking about review speed.

What the definition of “is” is
President Bill Clinton’s now famous remark serves us well in this discussion. What is it that we mean by review time? Does it mean that 375 e-mail messages that do not contain a particular search term and are bulk categorized as “non-responsive” constitute “reviewed”? That might take only a few minutes and may be a legitimate use case. Or, do we mean the traditional manner in which attorneys review documents by reading them in total? For lengthy contracts or complex spreadsheets, review time could be longer than a few minutes per document.

I like to start with my “theoretical” maximum. I calculate this theoretical maximum in the following way. Assuming a document is actually being viewed and assuming the fastest method of changing from one document to the next (in a sense throwing it up on the reviewer’s screen as quickly as possible) the time unit of 1 second per document is assumed as a maximum. If a reviewer can (and I’ve never met one who could) review one document per second for a solid 8 hours, we would have 1 doc/sec * 60 sec/min * 60 min/hr * 8 hr/day = 28,800 documents per day. This also assumes that each document was only 1 page long. As I said, this is a nice theoretical maximum, but nowhere near what a human being actually achieves during a document review. I provide this number simply because I have seen some vendors toss out numbers close to this for their reviewers. If a vendor does this to you, be sure and question their math.

Individuals in charge of electronic discovery matters need to understand that review times can vary and that there are good reasons why they should expect them to vary.

Variables in the mix
There are a number of variables that control review time per “document.” First, what is a document? If it is a three-sentence email, then we can expect reviewers to get through that quickly. If it is an Excel workbook with 20 worksheets, a reviewer will need more time.

If the review is taking place on-line, then the condition of the Internet will come into play. If software residing on a desktop with data files on a network share is the situation, then network infrastructure conditions will be important. Although most contemporary desktop computers are relatively peppy, the processor speed and RAM memory may have an impact.

The honest answer to the question of speed is that it all depends. Review speed depends upon many variables, some of which are outside of your control.

Inquiring minds want to know
While it is simple to say that review speed depends upon many variables, factors and conditions, individuals want to know what our experience tells us, and what they can reasonably expect. That is fair, and I will answer that question with a simple rule of thumb for determining review times.

The “200” rule
Often I meet with clients who just need a quick-and-dirty number for time to review documents. This might be simply to satisfy the curiosity of a managing partner or in response to an unforeseen question in a meeting demanding an immediate answer. I will caution that this number or method will never be exactly accurate, but it is easy to remember the rule when cornered and an estimate is all that is really needed. Never substitute this number for a more detailed analysis that provides a range of values.

Where does this “200” rule come from? I calculated it based upon my analysis of data and review times in prior electronic discovery reviews.

Here’s how it works: Take the number of gigabytes (GB) of electronic data that needs to be reviewed and multiply that number by 200 to arrive at the estimated number of hours to review. For example, 30GB *200 = 6000 hours will be needed to review the entire document set.


  • One reviewer reviews 250 documents per day
  • One document on average is 12 pages in length
  • One GB of data = 75,000 pages or 6,250 documents using our 12 pages per document assumption. (This is a number often cited as an industry average.)

Given these assumptions, we can now perform some calculations for our 30GB test matter:

  • 30GB * 6250 docs/GB = 187,500 documents to be reviewed (2.25 M pages)
  • 187,500 / 250 docs/day = 750 Days to review all documents
  • 750 days * 8 hours per day = 6,000 hours.

There you have it. The next time you are called upon to figure out how long a review is going to take you now have a quick method to estimate the time it will take to review your next electronic discovery job. As you are working with the variables, which are based on real-life electronic discovery engagements, it will be important to point out to those involved that a more detailed analysis will be necessary as more information about the matter becomes available.

ED Therapist

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