Mastering Burndown Graphs for Effective Forecasting
In the multifaceted world of software development, effective project management is crucial for success. This is often mistakenly translated to micromanagement and detailed upfront estimation, resulting in excessive time spent on planning and analysis and yet failing to make accurate forecasts.
In dynamic environments such as software development, where work is emergent and uncertain, teams need to rely on empirical data and shift focus towards adaptive strategies to optimize performance. Pressure to deliver according to some arbitrary upfront plan will often only stiffle progress.
The burndown graph offers visual simplicity and is by nature empirical and data-driven, helping to separate estimating effort from time based forecasting.
What is a Burndown Graph?
A burndown graph visually represents the work remaining in a project, and shows the team’s history of progress.
It displays completed work and tasks still pending. The graph features two axes: the x-axis represents time, and the y-axis represents remaining work.
How Does a Burndown Graph Work?
At the start, the graph is a dot on the y-axis representing the total effort at the start of the project. As the project progresses, the graph is updated by plotting remaining work on the x-axis, showing how work progresses over time.
After a few iterations, a trend emerges. This information can be used for forecasting and planning future iterations.
The line’s slope reflects the team’s progress rate, also known as velocity.
By examining the horizontal axis, teams can compare actual progress against the planned trajectory and forecast the project’s completion date, illustrated by the intersections of the line with the x-axis.
Benefits of Burndown Graphs
Burndown graphs offer several advantages to teams and stakeholders:
Visibility: They provide a clear, visual representation of progress, allowing stakeholders to easily see remaining work and track targets.
Motivation: Observing the line move downward is motivating for team members, offering a sense of accomplishment and encouraging momentum.
Improved Planning: By analyzing previous iterations’ progress and trends, teams can make better forecasts and set realistic future goals.
Helps Separate Estimations and Forecasts: By tracking progress using empirical data, the burndown graph helps separate estimation of effort and forecasts in calendar time.
Nothing is ideal It is essential to separate estimating and forecasting. So many other factors influence the latter, such as team composition, availability, customer feedback, environmental factors, etc. Teams are usually quite good at estimating effort, but no one can predict what will happen in the future. This is why teams sometime use the term “ideal days” to refer to effort estimates.
Leveraging Empirical Data for Accurate Forecasting
As mentioned above one valuable aspect of burndown graphs is the reliance on empirical data. By capturing historical performance, they provide a realistic basis for forecasting future outcomes. This approach, akin to “yesterday’s weather,” suggests that if a team maintains a certain velocity, they will likely continue at a similar pace.
Using empirical data minimizes subjective biases, providing a solid foundation for informed decision-making and setting realistic expectations. As a project advances, the burndown graph can show whether the team is on track to meet deadlines, allowing for timely adjustments and risk mitigation.
Facilitating Meaningful Conversations
Burndown graphs do more than display numbers and lines; they prompt important conversations. Data requires interpretation and discussion. Regularly reviewing the burndown graph and seeking to understand its development encourages open communication about progress, challenges, and potential adjustments needed.
These discussions are crucial for understanding the data. For instance, a dip in velocity might stem from unforeseen technical challenges, new customer requirements, or external factors. By addressing these issues collaboratively, teams can develop strategies to overcome obstacles and enhance performance.
Variants of Burndown Graphs
While the basic burndown graph is powerful, several variants add additional value.
1. Ideal Burndown
The ideal burndown line represents the required velocity to reach a deadline, for example the end of an iteration, or a release date.
2. Including Added Work
In software development projects, new tasks emerge over time, often referred to as scope changes. Including scope changes in the graph offers a more comprehensive view of the project’s evolution, showing not only completed work but also new work introduced.
It is common for the graph to trend upwards as large items are broken down into smaller tasks. This increase results from greater granularity rather than additional work. While this is expected, it should happen less frequently over the project’s lifetime. Being aware of this phenomenon is important, as it affects the accuracy of forecasts. Many project managers recognize this fact, which is illustrated in the uncertainty cone:
3. Forecasted Interval
Projection lines enhance the utility of burndown graphs by providing a future perspective. Based on historical velocity data, they indicate the project’s likely completion date.
The projection can be extended with a range that reflects a percentage-based positive or negative deviation from the current velocity. The points where these lines intersect the x-axis represent the forecasted completion date range.
The forecasted interval can be calculated using all empirical data or a rolling average of the last n iterations. The latter approach is often more realistic, as it reflects the team’s current velocity and prevents overestimating the forecast based on past performance.
4. The Burn-Up Graph
An alternative representation is the burn-up graph. This graph shows the same data but instead of showing remaining work, it shows completed work on the y-axis.
Potential Pitfalls and How to Avoid Them
It is important to use burndown graphs correctly to ensure their usefulness and prevent data misinterpretation.
Interpreting Progress Correctly
Interpreting data accurately is essential. A perceived lack of progress may not indicate poor performance; it could be related to factors such as technical debt or changing requirements. Effective leadership and an understanding of the factors influencing progress are crucial for making well founded informed decisions.
Estimating the Initial Workload
The initial forecast is one of the trickier parts of using burndown graphs, especially when using relative estimation and not having a yardstick or reference point. See the post on progressive planning for more on this.
The best approach is to begin with a rough estimate, start working, and revisit the forecast after a few iterations. It’s important to remember that the initial estimate is not a commitment and is inherently inaccurate.
Relative Estimates vs Number of Items
Burndown graphs can use different metrics for tracking progress, such as story points or simply the number of items.
In a project context, not all backlog items are known from the start. Work is typically represented by large items, sometimes called epics, which are broken down into smaller parts over time. This makes the number of items less useful. A better choice is to use story points or another relative effort-based metric.
Integrating Burndown Graphs into Project Management
To maximize burndown graphs’ benefits, integrate them into the overall project management strategy. Some recommendations include:
- Start Early: Begin with a lean approach, focusing on early iterations to gather velocity data, set realistic deadlines, and adjust plans as needed.
- Continuous Monitoring: Regularly update and review the graph to track progress, identify risks, and make informed decisions.
- Open Communication: Foster open communication where the graph’s data is collaboratively discussed, and decisions are based on collective insights.
Conclusion
Burndown graphs are invaluable in project management as they provide visibility and an early indication of velocity. However, their effectiveness depends on accurate data representation, which should not be confused with precise data. For more on the difference and the importance of accuracy, see the post on What is a good estimate.
The burndown graph clearly distinguishes between effort estimations (the y-axis) and forecasts (the x-axis). This distinction helps prevent the common mistake of confusing the two and asking teams to estimate in calendar time.
