You didn't mention your background, so I'll assume you haven't had any substantial Industrial Engineering or work process measurement training, and probably very little work experience in your field.
I hope your first step was to check out Value Stream Mapping on Wikipedia. I lifted the following from their site and edited it a bit.
Value stream mapping is a lean manufacturing technique used to analyze and design the flow of materials and information required to bring a product or service to a consumer. At Toyota, where the technique originated, it is known as "material and information flow mapping". It can be applied to nearly any value chain.
Shigeo Shingo suggests that the value-adding steps be drawn across the centre of the map and the non-value-adding steps be represented in vertical lines at right angles to the value stream. Thus the activities become easily separated into the value stream which is the focus of one type of attention and the 'waste' steps another type. He calls the value stream the process and the non-value streams the operations. The thinking here is that the non-value-adding steps are often preparatory or tidying up to the value-adding step and are closely associated with the person or machine/workstation that executes that value-adding step.
So first, clearly identify the process you are measuring and its desired outcome. Let's say you're working on the "Answering a customer's questions via email" process. The key
steps are probably:
- Customer email arrives (triggers the start of the clock)
- Wait for Customer Service to read email (NVA delay)
- Email is read by Customer Service (this is arguably value added, since the information is "Processed" by the CS rep - an online FAQ could eliminate the whole process for many questions)
- Wait while CS obtains an answer (NVA delay)
- CS replies to email (Value-added and stops the clock)
You have to be very focused on the difference between a step that is required and a step that adds value to the desired outcome or product. So, while obtaining an answer is required, it doesn't add value. In a perfect world, the answer would already be at CS's fingertips. The purpose of this process is to reply to the customer with a complete and correct answer. Any delays in doing so, including obtaining the answer, are NVA. But you probably already realize that.
I think it would work for you to think of your process as simply the above, but within the "Obtain an answer" step, you'll have a series of very similar, but NVA processes that repeat until a satisfactory answer has been reached. I wouldn't worry about exactly how long it takes to actually process the paperwork or for either CS or the Subject Matter Experts to read/answer emails. Those times will usually be dwarfed by the delay times. Ralph Long's reply about flow rate is correct, but it combines the waiting time and effort time so that it's usually harder to identify and eliminate the waste of waiting. In this case it probably doesn't matter. Improve the delay times and you'll get a huge improvement.
I'm afraid you may have to do some serious data mining of email threads and their time stamps. You'll need to cooperation of the customer service reps to access them. If you're able to have them log times on a data collection sheet, you'll be able to come up with answers much faster. Check with your boss on getting that backup.
Please feel free to send me a message if you have other questions.