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Lead
Lead is the acceleration of a successor activity. In other words, the second activity can begin (and be conducted in parallel) as the first activity.
Lead is only found activities with finish-to-start relationships: A must finish before B can start.
In order to leverage a lead, which will compress the total combined duration of both activities, the dependency must be discretionary, meaning that there is no physical limitation on completing A before B begins.
Lag
Lag is the delay of a successor activity and represents time that must pass before the second activity can begin. There are no resources associated with a lag.
Lag may be found in activities with all relationship types: finish-to-start, start-to-start, finish-to-finish, and start-to-finish.
Example
The photo shoot will take four days and the photo editing will take six days. Instead of waiting until the end of the4-day photo shoot to begin editing the pictures, we start editing after the first day of shooting. This brings the total duration from ten days down to seven days by leveraging the lead.
The photo proofs are sent to the customer upon completion of the shoot, however, there is a15-day lag associated with the customer review before the printing of the photos can begin.
Summary
Lead and lag are both used in the development of the project schedule.
Lead is an acceleration of the successor activity and can be used only on finish-to-start activity relationships.
Lag is a delay in the successor activity and can be found on all activity relationship types.
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LEAD sheet material used on roofs.
LAG. To be behind and not keeping up.
Lag to wrap typically hot water piping to retain heat there in.
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When developing a Balanced Scorecard (or any other performance management system), it is recommended to use a combination of Leading and Lagging Indicators. Kaplan and Norton call these “Performance Drivers” and “Outcome Measures”.
The idea is that Lagging Indicators without Leading Indicators tell you nothing about how the outcomes will be achieved, nor can you have any early warnings about being on track to achieve your strategic goals.
Similarly, Leading Indicators without Lagging Indicators may enable you to focus on short-term performance, but you will not be able to confirm that broader organisational outcomes have been achieved. Leading Indicators should enable you to take pre-emptive actions to improve your chances of achieving strategic goals.
Implicit in the design of any balanced performance management framework, such as the Balanced Scorecard (BSC), is the cause and effect chain of goals and strategies. So, “investing in organisational capability” leads to “efficient and effective processes”, which deliver the products and services that “satisfy customers” and ultimately lead to “profit” in the private sector, or “positive stakeholders/funders” in the public sector.
Because there is this cause and effect chain, there is a corresponding chain of Leading and Lagging Indicators. For example, “Satisfied/Motivated Employees” is a (well-proven) Leading Indicator of “Customer Satisfaction”. Similarly, “high-performing processes” (e.g. to6 Sigma levels) would be expected to be a Leading Indicator of “Cost Efficiency”.
Arguably, the BSC perspectives focussed on Organisational Capability (or Learning & Growth) and Processes contain Leading Indicators of external performance that are contained within the Finance and Customer perspectives.
However, it’s not as easy as that, because within each BSC perspective, you will usually want a combination of Leading and Lagging Indicators. For example, you are likely to want to measure “Employee Satisfaction” and could readily identify a Leading Indicator of this such as an index of “Leadership Capability”, or maybe “No. of days training per employee”.
It is sometimes said that Leading Indicators will be measured more frequently than Lagging Indicators, but that may not be helpful as a definition. You could measure “Complaints Received” or “Customer Satisfaction” every day, both of which might be described as Lagging Indicators. Equally, you could measure process “Error Rates”, or “On-Time Delivery” every day and these are probably Leading Indicators.
The view that Lagging Indicators cannot be adjusted until it is too late is also not necessarily very helpful. In the example above, knowing that you have an error rate of25% is already too late!
One definition that might help is that Leading Indicators are often captured at the level of individual processes, whereas Lagging Indicators may be the result of changes in a number of Leading Indicators. So, a process cycle-time or error rate might be Leading Indicators, measured at the process level and Customer Satisfaction would be a Lagging Indicator, measured at the organisation level.
If you are measuring “activity” (i.e. at a process level), it is more likely that you are using Leading Indicators. The closer you move to process inputs and activities, the closer you get to Leading Indicators of downstream, (Lagging) performance. If you are measuring aggregated effects, or outcomes, at an organisational level, you are more likely to be using Lagging Indicators.
Remember, the overall purpose of selecting metrics is to enable you to track performance towards your goals. So, you should aim to identify and then control those metrics that drive you towards your ultimate goals.
Precedence Diagrams help you to determine the project activity flow. Through the project activity flow, you can identify the critical path and compute the float of each activity. The schedule is created by using the Precedence Diagram and understanding the relationship between activities. It doesn’t mean the type of dependencies, such as Finish-to-Start, rather it means the relationship between two dependent activities. The concept of Lead and Lag is critical in defining this relationship.
Regardless of the type of planning methodology or technique, such as Agile or Rolling Wave, the concept of Leads and Lags is applicable.
Lead refers to a relationship whereby the successor activity begins before the predecessor activity has completed. For example, suppose you are baking a cake. As part of this, you will need to get the mixture ready and insert the dish into the oven. “Get the Mixture Ready” is the predecessor of “Insert the Dish into the Oven.” Pre-heat the oven is a task that is a part of the “Insert the Dish into the Oven” activity. Therefore, the “Insert the Dish into the Oven” activity should start before you’ve completed the “Get the Mixture Ready” activity. Assuming the pre-heating takes20 minutes, then the “Insert the Dish into the Oven” activity should start20 minutes before you have completed the “Get the Mixture Ready” activity. Therefore, the “Insert the Dish into the Oven” activity has Lead of20 minutes.
Lag refers to a relationship whereby the successor activity cannot start right after the end of its predecessor. For example, after you’ve baked the cake, you might want to serve it cold. Therefore, before serving it to the guests you will need to put the cake into a fridge and wait for it to cool. This means that the activity “Serve Guests Cake” will not start right after its predecessor “Insert the Dish into the Oven.” There is a delay. This delay is called Lag.
Hope that answers your question well.
I support the comprehensive answer of Mr. Jetley on Lead and Lag.
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Thank you
