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September 1999

Darwinian Call Centers


Darwin would have felt at home in a modern call center. He would have been able to study its constantly evolving nature and see his theories in practice.

Modern call centers are places of continuous change. The technology changes as new ACDs, IVR and other CTI advancements become available. Call centers also often have a high turnover of people, and new agents may be recruited for new or expanding services. Perhaps most significantly, the workload changes - in volume, incidence and nature. Every day is different from the last, next week will be different from this week and six months from now...well, who knows? New services, increased opening hours and promotions all contribute to evolutionary, and in some cases revolutionary, change.

How does the call center manager manage all this change? A plethora of tools are available, most of which are technology-driven. Tools such as complex call routing scripts, real-time displays, call analysis and agent monitoring offer the promise of increased efficiency and customer satisfaction. But how does the manager allocate the personnel to meet these constantly changing needs?

In a majority of cases, all or most agents in a call center work fixed shifts. They do the same duty every week, often with the same start time and the same days off. Agents may even go for their coffee and lunch at the same time. This custom has usually evolved from a less demand-driven environment. Over time, the workforce has increased to meet an increasing workload, but the placement of people to shifts is done on the basis of covering either early or late shifts. This practice can work very satisfactorily in an office environment, but in a call center it is less than optimal. Why is this so?

The Curse Of The PCA
Most call centers have quality of service targets the managers are asked to meet. These targets are a means of measuring the service offered to customers. How easily and quickly does the customer get through to an agent? How easily the customer gets through is usually a hardware issue — is the service freely accessible? How quickly the customer’s call is answered is usually measured by the percentage of calls answered (PCA) within a specific time interval, termed the service objective (SO). For example, a PCA80/20s target specifies that 80 percent of calls are answered in 20 seconds.

Typically, in a call center, the PCA target is in the range of 80 to 90 percent and the SO is 15 to 30 seconds. If we look at an example of the relationship between the number of agents and the achieved PCA, the result would be as shown in Figure 1.

Using this graph, we can see that providing a PCA of 80 percent would require 17 agents. If the service was under-provided by two agents, the PCA would drop to 53 percent, a decline of 27 percent. If the service were over-provided by two agents, the PCA would only rise to 94 percent, an increase of 14 percent.

This demonstrates that the relationship between PCA and agent provision is nonlinear. If the call center is understaffed for a period, the fall in the PCA cannot be recovered by overstaffing by the same number for some other period. It is crucial that staffing be configured as closely as possible to the requirement at all times. If it is not, then the only way of meeting service targets is by overstaffing — and that costs money.

How Flexible Are You?
There are a number of areas where flexibility in working practices can bring rewards. How many of these statements are true in your call center?

  1. My people go for breaks and lunches at the same times every day.
  2. My people go for breaks and lunches at the same times every week.
  3. My people start at the same time every day.
  4. My people start at the same time every week.
  5. My people work the same days of the week every week.
  6. My people work the same number of hours every day.
  7. My people work the same number of hours every week.

Why Be Flexible?
Consider this example: The following is based on a call center that is open from 8:00 a.m. to 6:00 p.m., Monday to Saturday. The agents work a 40-hour, five-day week. There is a 30-minute lunch and two 15-minute breaks each day. The starting times of the shift were initially fixed as being the same each day of the week. Schedules were then produced to meet the forecasted demand. The rules were then changed to allow the starting times for any shift to flex up to one hour within the week. Figures 2, 3 and 4 illustrate the fit of agents to calls on Monday, Wednesday and Saturday. As can be seen, the fit of agents to the requirements is much closer when the starting times of agents are allowed to be different on different days during the week. The reason for this can be seen in Figure 5.

The incidence of calls is such that requirements vary from day to day. Not only does the volume vary, but also the pattern of arrival changes from day to day. If starting times are fixed over the week, it will restrict the accurate placement of people to meet the changing demand. The same holds true for the allocation of breaks and lunches. The ability to vary the lunchtime from one day to the next will increase the ability to meet different incidence patterns of calls.

Now consider another aspect of call arrivals — the change in distribution over time. Figure 6 shows the call incidence for two Mondays, 13 weeks apart. The graph shows the pattern of call arrivals has changed over time, even though the volume is very similar.

If agents’ schedules are fixed on a roster for a set period, then the fit of agents to calls will be optimal only for the first week of the roster. After that date, there is a high probability that call incidence will change. It may not appear significant, but Figure 7 shows the increase in deviation using fixed shifts. As we have seen earlier, a small loss of accuracy can have a large effect on service. The ability to redefine shifts on a regular basis can help ensure optimal staffing.

The purist’s viewpoint would be that since a call center is a constantly changing environment, as much flexibility as possible should be introduced to allow the center to continue to meet customer needs. This maxim should apply not just to personnel but to all elements, including management.

In practice, a number of constraints will come into play, not the least of which is agents’ morale. This should always be considered carefully before making changes to working practices. Often the changes that occur in the short- to medium-term do not necessitate full work flexibility for all staff. Most of the benefits described above could be realized by introducing more flexible shifts for 10 to 20 percent of the workforce. However, the possible benefits are quite tangible. Introducing flexible breaks, start times and week-on-week changes could each improve the PCA by 1 to 2 percent. This translates into 1 to 2 percent savings in personnel costs.

And that is worth thinking about.

Dennis Cox is the managing director of PIPKINS UK, Ltd., the European headquarters for PIPKINS, Inc. Dennis worked for thirteen years as a workforce efficiency manager at BT (formerly British Telecom) before coming to PIPKINS in 1992. One of his main areas of expertise is the effective integration of workforce management tools and human resources. PIPKINS is a supplier of workforce management systems and services to both United States and international call centers. PIPKINS, Inc. is headquartered in St. Louis, Missouri, with its European Headquarters located in Yorkshire, England.

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Figure 2
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What Difference Does One Person Make? Understanding Call Center Staffing And Service Tradeoffs


Whether manually created or developed through workforce management systems, carefully devised workforce schedules must be adhered to strictly. This is critical to your business. However, getting agents to adhere to their daily work schedules is one of call center managers’ biggest challenges. Many agents think, “There are dozens of other people on the phones now. What possible difference would it make if I just log-off a few minutes early for my break? Just one person can’t possibly make that much difference.” Sound familiar?

In many cases, a little education can improve schedule adherence. Helping staff understand the impact that an individual agent’s actions have on service can go a long way toward getting them to stick to their assigned schedules.

So just what is the impact of a person or two on service? Well, it depends. The impact on service depends largely on two factors: the size of the call center and the current level of service delivery. Obviously, the smaller the call center, the greater the percentage share of workload handled by each person, and, therefore, the bigger the impact of his/her participation. For example, if we look at call centers achieving a 30-second average speed of answer (ASA) with 10, 25 and 50 agents, and then take away one agent, the smaller operations will be most affected.

The economies of scale of the larger call centers ensure a greater efficiency in the call-handling process, therefore the impact of one person is not as significant for them.

The other factor that determines the impact on service of any one person is the level of service currently being provided. The better the existing level of service, the less the impact of one person, as illustrated in Figure 2 (using the example from Figure 1 of 346 calls per half hour, 240 second average handle time, or 46 Erlangs).

Obviously, as staff numbers increase, service improves. As staff numbers decrease, service worsens. Depending on where the call center currently falls in the staffing/service curve, the impact of one person could be minimal (for example, going from 54 to 53 staff worsens ASA by only two seconds). On the other end of the spectrum, decreasing staff from 48 to 47 staff handling the same calls would deteriorate service from a 91-second average wait to nearly 4 minutes.

The good news about one person’s impact on service is that if your call center is in a service slump, adding just one more person on the phones can result in a tremendous improvement. On the other hand, losing one person in what is already a mediocre or poor service situation can ruin service for that period of the day.

Knowledge Is Power
A few charts and graphs illustrating the above staffing/service relationship in your next staff meeting should help enlighten those agents who think their impact on service is insignificant. Simply educating agents about the effect on service that one or two bodies can have will help them understand the importance of schedule adherence and increase their cooperation with the scheduling process.

Penny Reynolds is a consultant with TCS Management Group, Inc., which specializes in providing workforce management solutions and consulting services to call centers of all sizes and configurations. Call centers use TCS workforce management software to forecast call volume, create and assign work schedules and track performance.

Figure 1. The Impact of One Agent On Service

57 calls/half hour
10 agents
30 sec. ASA

163 calls/half hour
25 agents
30 sec. ASA

346 calls/half hour
50 agents
30 sec ASA

Minus One Agent:
9 agents
83 sec. ASA

24 agents
58 sec/ ASA

49 agents
50 sec. ASA

Figure 2.  Individual Impact On Service Level

Number of Staff

Actual Speed of Answer

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