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August 2009 | Volume 28 / Number 3
Ask the Expert

Short Message Service (SMS)

ACD Routing Best Practices LIFO vs. FIFO

By Tim Passios,
Director of Product Management, Interactive Intelligence

Being first in line is usually perceived as being equal with "greatness". As a parent, I often see how this perception plays out in the lives of my two young children each has to be the first to get ice cream, see the movie, open gifts, ride in the front seat, etc. Whenever one of them ends up second, a temper tantrum ensues, along with the complaint of how unfair everything is.

It isnt much different as an adult. Even if its only a video game, not being first frequently leads to the same frustration. There is one exception, however, and strangely, its when youre a customer calling a business.

Sometimes, being the last caller in line is actually better than being first.

A few years ago one of our customers spoke at the annual Interactive Intelligence User Conference about a change they made for routing calls in their contact center. Not long after the change, their customer satisfaction ratings increased dramatically. What did they do? Instead of routing calls using the commonly accepted First-In-First-Out (FIFO) methodology, they began using a Last-In-First-Out (LIFO) approach.

I remember sitting in the audience thinking, "Did I just hear that correctly? Youre actually giving higher priority to the last caller versus those whove been waiting the longest?"

Our invited speaker had my attention, and got even more of it as he summed up why the FIFO to LIFO change was so impactful:

"If you dont know the truth, your perception is all you have to go on."

In essence, with LIFO, callers who called in last were answered first, and their perception was one of excellent service, chiefly because they werent placed on hold. Favorable survey scores could, therefore, be expected afterwards. Conversely, for customers who called in first and had to wait via the LIFO method, they knew no different and assumed their wait time was normal. Survey ratings for those callers, then, would likely be lower, but not terribly low.

Lets compare perceptions. Use FIFO routing in which callers routinely expect at least a short wait time, and poor survey ratings are the norm. Implement a LIFO approach, and the perception is just the opposite: callers know theyll sometimes have to wait, but also know the chance is good that service will be rather quick, if not immediate.

See the difference?

To find out if other contact center veterans agreed with the LIFO routing changeup, I posted the information on our blog site to see if it would solicit any thoughts. I asked blog readers if there were any caveats to running the LIFO methodology in all contact centers. I also wondered about the impact on calls where the average talk time is high? And what about call volume does higher traffic cause problems? What about seasonality spikes? I asked readers to think of any factors that would affect their decisions to deploy LIFO routing.

The answers were interesting. While most respondents felt LIFO routing was definitely the better methodology, there were definitely some areas of concern.

One of the biggest was customers getting stuck in the queue. "The only thing that would worry me," one respondent said, &would be during those times of high call volume. When your queue builds, those customers who were holding would wait even longer because newer calls would enter behind them and would continue to get answered first." Good point.

Another concern with LIFO was abandons. "Some people, when holding for a while, will hang up and call right back only to find out they get answered right away. Once customers know they can get faster service by hanging up and calling in again, your abandons would go through the roof&" Good point again.

To me, it seems the solution to both concerns for LIFO routing would be to set a threshold that monitors wait times and moves calls up in priority after they had waited for X minutes. This would ensure that callers would be the next call to get answered, creating a balance between customers being answered quickly and customers waiting for a short period without greatly impacting abandoned calls. This would also help set proper customer expectations in line with “sometimes I get answered quickly, but if I do have to wait, its never more than X minutes".

Have a few ideas on LIFO and FIFO routing, or some other type of routing methodology? Visit our blog site at

Tim Passios is Director of Solutions Marketing for Interactive Intelligence, Inc. and has more than 18 years experience in the contact center industry. Interactive Intelligence is a leading provider of IP business communications software and services for the contact center and the enterprise, with more than 3,000 installations in nearly 90 countries. For more information, contact Interactive Intelligence at or (317) 872-3000.

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