Wednesday, 27 May 2015

Where the Bradford Factor goes Bad

This article was prompted by a story in “The Guardian”:

“You are a healthcare professional working with elderly people. You really have no business being at work because your throat is sore and inflamed; you feel febrile and have a cough. In short, you are going down with something which is, at best, a cold - but may be flu.”

“Exposure to the illness would be potentially lethal for your frail patients, but sick leave could result in you facing a formal occupational health or disciplinary hearing. You are on the horns of a dilemma already facing many health workers this winter, but one which will soon face many more.”

““This is the "Bradford factor", a system for differentiating longer, infrequent staff absences from those which are more frequent, but of shorter duration. The assumption behind it is that high frequency, short duration absences are more problematic in certain types of organisation, are symptomatic of different problems and require separate identification in order to be addressed.” (1)

How does this work?

The Bradford Index equals the number of spells of absence in the last 12 months squared, multiplied by the number off days off - (SxSxD)

So by way of example:

one absence of 14 days is 14 points (i.e. 1 x 1 x 14)
seven absences of two days each is 686 points (i.e. 7 x 7 x 14)
14 absences of one day each is 2,744 points (i.e. 14 x 14 x 14)

It is a common tool in use by Human Resources department, and apparently originated during the 1980s with a connection to the Bradford University School of Management. However, I have been unable to track down any provenance for it.

In fact, another individual who investigated found this was a Dr Geoff Helliwell who noted:

“IDS first referred to the Bradford factor or formula in Study 365 published in July 1986. That publication included a reference to the use of `Bradford' factor point scores by May & Baker (now Rhone Poulenc Rorer). Contacts at the company say that this method of calculating absence rates had been introduced as a result of managers attending a series of seminars on production management arranged as a part of a Bradford University management course in the mid-1980s. Controlling absence was one of the management areas that was covered. However, as you discovered, if you contact Bradford University's School of Management they know very little about it and I have never come across any published record of its academic origins.” (11)

Insofar as it appears anywhere in literature, Dr Helliwell found that the earliest mentions were: IDS Study 365, 'Absence', July 1986, page 5, IDS Study 498, 'Controlling Absence', January 1992, pages 3/4 (successful use of the formula at Victoria Coach Station), IDS Study 556, 'Absence & Sick Pay Policies', June 1994, page 6. He notes that a description of the factor also appears in `Measuring and monitoring absence from work' published by the Institute for Employment Studies in 1995, although its origins are not given.

This is a singular deficiency, because how it was created, what rationale lay behind the squaring of number of spells of absence, and if it was ever peer reviewed in any academic journal, is not available. In fact, as far as I can ascertain, it never has been subject to academic scrutiny in any peer reviewed journal or featured in any books on statistics.

In that respect, I find myself in agreement with a report made by Robert Perrett and Miguel Martínez Lucio in June 2006, ironically from the Bradford University School of Management, the supposed origin of the formula.

“An individual who has two spells of absence of five days in duration accumulates just 40 Bradford points, whereas a colleague who has five spells of absence of two days accumulates 250 Bradford points and is reprimanded. Use of such formulas is common. Others formulas exist in an attempt to differentiate types of absence and to provide them with a scientific rationale. Many of these formulas use spurious evidence and research, and are sometimes even difficult to identify in terms of originating documentation, but this has not deterred many organisations from using them”” (2)

The study noted that it was used as a disciplinary tool targeted at employees who played the system and were absent frequently. It is known that sick leave can be abused by employees, and that this is often short term, just the odd day.But odd days can mount up.

“Overestimating the extent of abuse can result in the implementation of harsher punitive measures that can actually result in an increase in absence rather than a decline. This was witnessed in one of the case studies undertaken. Almost half (47 per cent) of respondents believed that employees with genuine illnesses had been penalised because of the absence provisions (41 per cent did not believe this to be the case and 13 per cent were unsure) furthermore, 44 per cent of respondents claimed that sickness records formed part of an employee’s appraisal. “

“Penalising genuinely ill employees, immediately following absence or later through an appraisal system, can create a range of negative repercussions for the employee and employer alike”

And this leads to significant problems like those highlighted in the Guardian article:

“For example, employees might feel compelled to go to work to avoid being reprimanded, potentially spreading diseases. This will also have a negative effect on productivity, moral, motivation, and the desire to remain employed with the organisation.”

Philip Taylor is a Professor of Work and Employment Studies and Assistant Dean International at the Strathclyde Business School at the University of Strathclyde. He has also examined the cultural shift which has taken place:

“Taylor also points to the way in which the management of sick leave over the past two decades has become more draconian with short-term illnesses penalised through the “Bradford factor”, the use of return to work interviews and discipline and dismissal triggered by particular levels of absence. The effect of this in the workplace has been to institutionalise bullying as layers of managers are forced to “cascade” pressure to workers below them to meet targets.” (3)

Part of the problem is the focus on number. If we were to examine the Bradford Factor properly, using scientific methods, then we would have to look at the following:

What is the likelihood of any short term absence being spurious?

The Bradford factor has an inbuilt assumption that short term absences are either spurious or reveal an underlying health problem. There is no means of differentiating between the two.

For example, it cannot factor in predictable short-term absences: as for example, time off every week for treatment or counselling. The employer should accommodate this if it cannot be done outside working hours.

Nor can it deal with unpredictable short-term absences which may happen often/for a variety of reasons such as an underlying medical condition or poor immune system. This may lead to the employer suggesting an employee work flexible (or zero hour’s contract) or lighten or vary the workload for a particular period.

Now it may be argued that a high Bradford score is a good measure for identifying the basic short term absence, but the problem arises what to do when you know the reasons for the absence, because the calculation now tells you nothing more than what to expect.

In fact, a more granular computation, and one which didn't rise so spectactularly, would be to take a sum of Bradford Factors of different counts, so that a count of 1,1,2 - Bradford score on 3x3x4 = 36 would instead become 2,2 and 1,2, being 2x2x2 +1x1x2 =8+2=10. This would still isolate smaller days off but would differentiate better between them.

And it also does not help with understanding how absenteeism affects the business. Compare Tom who takes seven days off in one hit to recover from an injury and has a Bradford score of seven with Cally, who takes six absences for minor illness over six days with a Bradford score of 216.

Now if it was, for example, a business which specialised in bureau work book keeping. 25 days spread out over a year is not so critical, because the employee is back on the following day. 25 days in one go might be critical, especially where payroll functions are concerned.

But because the focus is on the high score, and not the nature of the business, this is not seen. In fact, a scoring method which rated longer periods of absence – say Tom plays rugby in his spare time, and has a few spells off - would actually be more useful.

Moreover, I have seen only one case where the Bradford factor has been analysed to look at systemic factors, type of work, different workplaces, so that a normalised benchmark can be visible. If systemic factors are causing workplace illness, then it is the workplace or working practice rather than the employee which needs to be addressed.

The return to work interview is a method of getting more information about the kind of illness, more than purely the bare bones of a Bradford figure. But the problem arises here insofar as it can be conflicted. As Phil Taylor points out:

“Return to Work Interviews (RWIs) became the most frequently utilised procedure. In practice, RWIs conflate caring and welfarist intentions (soft HRM) with calculative and disciplinary motives (hard HRM), but, principally, they reflect the latter and the impact of US thinking on occupational health, which emphasises getting people back to work rather than the employment problems that might have made people sick in the first place” (4)

The conflict here is between the use of the return to work interview as caring for the employee, and using it as a means of disciplining the employee.

The Employment Law Clinic notes this:

“Remember, this is a return-to-work Interview, not a disciplinary hearing (if a disciplinary becomes appropriate, deal with this separately, and in accordance with your disciplinary procedures)”(5)

As another site notes:

“Make sure the conversation with the absent employee is clearly focused on their well-being and their return to work. Try to focus as much on what the employee can do as things they may need help with. Returning to work is an important milestone in getting life back on track, but if the employee is made to feel a ‘problem’ in some way, they will feel disheartened.” (6)

However, in practice it may be almost impossible to construct a Chinese Wall to prevent the return to work feeding into a disciplinary, even if they are held separately. This is very clearly seen in the HROnline Website:

“From a motivational point of view, there’s evidence that companies that impose RtW interviews experience a reduction in sickness absence. There are a few reasons this could be case. First, it shows that you are taking absence seriously; that your company is taking some sort of action on absence. But second, there’s a “fear factor” involved – some employees who might in the past have taken the odd day off when they simply couldn’t be bothered to come to work might be wary of being “found out” if they slip up in the interview by contradicting their original cover story.” (7)

Clearly absenteeism is an issue that needs to be addressed, but the use of the Bradford factor as somehow more than a mathematical artefact, coupled with the “fear factor” for a return to work interview, can inculcate a hermeneutic of suspicion which is not healthy for the workplace.

As someone who has worked conducting interviews notes:

“A return to work interview is where your line manager meets with you after you have been absent (sickness, unauthorised absence, sometimes even lateness). They will sit down with you and have 'an informal chat' which involves them ticking boxes on a form and asking you how you are in a kind and caring manner (i.e. asking for answers to a set of preset questions then writing everything you say down)”

“I've had to do return to work interviews in call centres and admin jobs many times over the last 10 years, I was also a line manager in an office for a while and had to do them on other people (look, I was young and I needed the money, OK?) They are part punishment, to make you feel like you have to come up with a good explanation for your actions, (like not doing your homework at school), and to reinforce the authority of your line manager as they become the embodiment of the Divine Right of The Company (a bit like scrofula).” (8)

HR Magazine has an interesting interview with James Arquette:

“James Arquette, director at absence management company, FirstCare, is not a fan of the Bradford scale. He feels it doesn't place enough emphasis on why an absence has occurred, which is what employers and managers must look at to determine how to support members of their team. "Ultimately, it is the action of employers once they have absence data that will allow them to manage absences most effectively," says Arquette. "The Bradford scale is far too reactive, whereas a policy based on sensible 'triggers' - a specific number of stress-related absences - can allow employers not only to identify a problem, but to step in proactively and provide appropriate support."

In conclusion, the Bradford factor is a blunt tool with inbuilt assumptions about patterns of absence from the workplace. The idea that its numbers are neutral and therefore unchallengeable is quite frankly nonsense. Other computational methods can provide better answers and more granular detail.

There is no theoretical basis for that assumption presented as a hypothesis and tested, with results public in a peer review journal, not is there any other comparison with statistical patterns such as Poisson distributions.

What I would expect to see is some kind of paper like “Multiple Approaches to Absenteeism Analysis”

“This piece compares eight models that may be appropriate for analyzing absence data. Specifically, this piece discusses and uses OLS [Ordinary Least Squares] regression, OLS regression with a transformed dependent variable, the Tobit model, Poisson regression, Overdispersed Poisson regression, the Negative Binomial model, Ordinal Logistic regression, and the Ordinal Probit model. A simulation methodology is employed to determine the extent to which each model is likely to produce false positives. Simulations vary with respect to the shape of the dependent variable's distribution, sample size, and the shape of the independent variables' distributions. Actual data, based on a sample of 195 manufacturing employees, is used to illustrate how these models might be used to analyze a real data set”

Another piece is “Markov chain Monte Carlo analysis of underreported count data with an application to worker absenteeism”(1996) – “A new approach for modelling under-reported Poisson counts is developed. The parameters of the model are estimated by Markov Chain Monte Carlo simulation”

These are solid pieces of statistical research using sophisticated but standard techniques for modelling absenteeism. They can determine patterns that are endemic in the population or workplace as a whole and provide benchmarks for comparison. By contrast, the Bradford factor appears in no mathematical statistical studies. The absence of the terms "false positives" or "significance testing" from any promotions of it on HR sites should flag up a red warning that this is a statistically crude method.

As Trevor Blackmore notes succinctly, the Bradford factor has a

“very dubious pedigree. Recent enquiries to Bradford University came up blank as to who proposed this statistical monstrosity. No reliable, scientific evidence as to its effectiveness over other methods. No RCTs, no factor analysis, nothing - only unreliable case study evidence comparing a couple of years data within a few companies measuring very limited outcomes.”

That, of course, doesn’t stop people using them or believe because they crunch out numbers that they are somehow “scientific” any more than it prevents people using the Stanford-Binet IQ test, the Myers-Briggs Type Indicator, or any other pseudo-statistical measuring techniques.

The promotion of the Bradford Factor has the blurb – “Absence Management Made Simple”, which should be warning enough, although simplistic would be a better term, and probably explains why it has had such wide take up by Human Resources departments and not by professional statisticians.


.(2)   Preliminary results from a survey of UNISON safety representatives: Interim Report, June 2006, Bradford University School of Management

.(3)   Taylor, Philip, 2012, “Performance Management and the New Workplace Tyranny”, Report for the Scottish Trades Union Congress, available from

.(4)   ‘Too scared to go sick’—reformulating the research agenda on sickness absence, Phil Taylor, Ian Cunningham, Kirsty Newsome and Dora Scholario, Industrial Relations Journal 41:4, 270–288


.(9)   Sturman, M. C. (1996). Multiple approaches to absenteeism analysis



Póló said...

This Bradford thing is a spurious statistical justification for managerial laziness.

Rulers/managers are ever trying to distill analysis into a single figure. The same is true of targets. The net effect is to distort and undermine the system of management.

I am familiar with the spurious idolatry of statistics from a bygone era.

Break your heart.

Nick Palmer said...

I once spent a whole year "discharging" a past (unreasonable) Bradford factor assessment. This involved me turning up at work about three times over the year with coughs/sneezes that probably infected others and reduced the quality of my work and left me washed out for a while afterwards.

It is my opinion that the rise of HR departments, the nunbers of staff "required" and the often spurious (IMHO) ideology that goes with them, is one of the worst things that has happened in the employment arena.

While not disputing that some of their functions, such as assorted employment admin etc, is useful, nay, vital, I have long held the opinion that it is HR depts and specifically their recruitment procedures and activities in this area, which are responsible for the seemingly incorrigible reinforcement of toxic managerial structures and attitudes.

It is HR departments who recruit the civil servants and chief officers who turn out to have rogue tendencies. When infilling "lower" jobs they tend to recruit those who will fit in to the existing system instead of those who would shine brighter in a better system but would make waves in a less good or bad system. I think that modern recruitment methods have the disastrous effect of disciminating against talented, really valuable, people in favour of company wonk "middle men" box tickers and those who school themselves in interview passing flimflam and manipulating office politics.

In short, if an existing system is crap. HR departments can often prolong that whilst simultaneously erecting barriers against those who might initially cause some disruption but would ultimately improve things.

bethanyemily haynes said...

the bradford factor should be for people throwing sickies not genuine illness if you have a doctors note is that not genuine where i work we come to work ill as scared of being fired should not be like this and one employee was told if she had the operation she needed to make
her better she would be fired as she had had time off with a related illness now the poor lady is very ill and has to give up work if she had had she op she would have been better able to work i feel this is playing god with peoples lives employers should not have the right to make you choose between your job or your life shame on you

Nhs employee said...

The Bradford score system makes my blood boil. Last November 2015 I had surgery on my foot, unfortunately it went wrong so had more surgery in January 2016. Now because I had had some time off sick in the past 12 months my Bradford score went through the roof! I had a"talk"with manager and of course now it's on my record of 18 years working for NHS. This is not how the Bradford score was supposed to be used. A colleague had a hip replacement, problems arose and she was onto the 2nd stage of disciplinary action. Extremely upsetting and worrying for those concerned. There is so much concern within the NHS that taking holiday instead of sickness is now happening, how can this be right ?
Extremely mystified NHS employeek.