Are Percentages Always Better Than Counts to Measure Performance?
Stacey Barr
Performance Measure & KPI Specialist ? Author of "Prove It!" & "Practical Performance Measurement" ? Creator of PuMP
The debate continues about whether percentages are always better to understand performance, rather than counts.
I've written a little about when to use counts versus percentages already. But with the persistence of debate about when to use which, it needs a deeper dive.
In the media and in politics, counts are often preferred over percentages. Perhaps our brains process counts better. Or perhaps counts make size much more apparent. And certainly there will be some that choose one over the other for dramatic impact or influencing power.
Road accident statistics are a case in point. There has been endless debate in the media over recent months about the apparent dramatic increase in motorcycle deaths on Australian roads. Those who use counts of deaths claim a 42% increase in the number of deaths. Those who use percentages of deaths relative to registered motorcycles argue that there has been a 35% decrease in the rate of deaths over the same time period. Australian Motorcycle News put a spotlight on this debate.
Why does it matter? It matters because it's metrics like these that influence policy and funding. If it's true that motorcycles are now at higher risk than before, then it warrants more funding to understand why and do something about it. But if it's true that motorcyclists are safer now than before, why take money away from a more needy cause?
I believe that measurement is to help us get closer to the truth, but it won't ever be the full truth. When we use counts and percentages, it's therefore vital that we understand the limitations of each, and the nature of the question we're trying to answer with them.
Counts are simple to produce and make it easier to comprehend size. When our focus is to reduce the existence of something we don't want, or increase the existence of something we do want, a count might be all we need. We don't want more motorcyclists dying on the roads. But counts do have some very specific limitations:
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Percentages do account for context and are less sensitive to limited comparisons (but not immune to them). When our focus is to decrease the chance of something we don't want, or increase the chance of something we do want. We do want to reduce the risk of any motorcyclist dying on the roads. But percentages also have some limitations:
Are percentages always better than counts to measure performance? Often they are, but not always. It's more important to understand the thing we're trying to improve, and triangulate measures to get convincing evidence about it.
Percentages don't ignore context like counts do, but should we always replace counts with percentages to measure performance? [tweet this]
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The post "Are Percentages Always Better Than Counts to Measure Performance?" was first published by Stacey Barr on https://staceybarr.com/measure-up.
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2 年The whole point of measurement is to inform decisions and actions. A point in time measure, even if it is a ratio or percentage, misses important context: how is it related to the (implied?) target, and how has it evolved over time? I would generally favour ratios and percentages, but there are times when counts are very good for motivational effect, eg “get to 10” or “get to zero”.
Retired Senior Advisor at Bank of Tanzania
2 年I think % are a better presentation and easy to give a picture of what the situation is, relatively. Giving a count to indicate performance does not show how significant it is without comparison to a another count. For example, Osaka prefecture in Japan decided in 2006 to develop a system to enable parents track their children to be sure they are in safe areas. The decision was made because 'too many' kids were being kidnapped. I was told 2 kids were kidnapped in 2005 when I asked. Coming from Africa where there a plenty of kids, 2 kids wasn't really a count that can raise many heads to require urgent action. But in Japan, where some kindergarten classes were closing and a primary school for 300 pupils had only 60 because there weren't kids to enroll, 2 kids kidnapped for a year was too much. However, if that count of 2 kids kidnapped for a year would have been understood by anyone if it was presented as a percentage of kids attending school.
Owner and Managing Director at NSP Strategy Facilitation Ltd
2 年As James rightly says KPIs are 'indicators of performance.' In most cases the KPI that you pick depends on the question that you want to answer. If you want to know how many units you sold this year, then the absolute number makes sense. If you want to know if sales volume is up or down on last year then expressing it as a percentage probably gives a better insight. It's all in the context of the issue, not based on right or wrong between absolute and percentage.
Transformation | Agility | Strategic planning & performance | Data analytics | Business intelligence| Business process management | Business excellence | Consultant | Coach
2 年Toraly Agree, & i beleive that KPI usability can resolve this kind of dispute, specially when you assess how decision takers use the KPI to make their business decisions
Management Consultant, Advisor, Researcher and Author.
2 年Always a difficult one. But I think it misses the point. Only through proper analysis of the data can we get the full story. No KPI can do that. KPIs are simply an indicator of performance (hence the name). Valuable, of course. But not the holy grail of performance management.