Working Theory - When and how should project planners think about sick days?
What is the impact of time out sick on tech projects?
Working Theories are semi-polished concepts and ideas that I’m screwing around with.
I was talking with my partner the other day and she mentioned that three of her team’s engineers were out sick and I off handedly remarked that it seemed like people were getting sick more often after COVID. Turns out I was right.
According to the U.S. Bureau of Labor Statistics, every January from 2012 through 2021 roughly three million people would miss work at least once due to illness. In Jan of ‘22 that number increased to 7.8 million, 2.6 times as many people.1 Fred Schott has been keeping an eye on this for a while using the BLS’ Annualized Absence Rate data2 and looking at his snapshots it seems like we’re experiencing a 10% enduring increase in sick days post pandemic.
This got me thinking; when and how should project planners think about sick days?
In the USA, the CDC claims that adults average one common cold a year3, meanwhile the Mayo Clinic says two to three colds a year4 and John Hopkins says two to four per year5. That gives us a range of between one and four colds/year per person. The same sources provide us a range of duration as well, Mayo Clinic says seven to ten days while John Hopkins says “several days to several weeks”. In my head this says seven days to twenty one days out. I couldn’t find good statistics for the distribution curve within that range though. So I made up my own curve, 25% are sick for a week, 50% for two weeks and 35% for three weeks. These numbers are intentionally pessimistic because, well, project planning. When you roll all this together you get a pretty neat thing: on average, you can expect an 8% drag on productivity from sickness. Sadly, averages hide a lot of things.
Let’s start with the impact of sickness on other employee’s productivity. Odgerel Chimed-Ochir et-al out of Japan published a study in August of 2019 that states: “Overall, employees lost 7.65% of their total working days, or an average of 17.92 days were lost per employee per annum, due to sickness leave and sickness presence combined.”.6 Only 1.1% of that was people actually leaving the office, the remaining 6.55% was what they call “sickness presence”, aka your coworker giving you a cold and dragging your productivity down. This study was done in Japan though and their work norms are a bit different, that said I’d wager that folks in the USA may have different reasons for working while sick, but that the rate is probably pretty similar. That means we can reasonably expect to pay this 6.55% productivity tax whenever someone gets sick. When you add this in, the average loss of productivity from sickness jumps to 12%.
These averages are hiding a few other things though, like what happens when someone on the critical path gets sick. That can have cascading effects, but the big questions are figuring out how likely that is, whether it’s going to happen, and what to do if it does happen. Here’s a few quick rules to help you out:
Sickness scales with Calendar Days and People, the longer your project goes in calendar time and the more people you have involved the more likely you’ll have an illness.
For every 183 Calendar-People-Days, you’ve got a statistically guaranteed chance of illness when you consider the average statistics.
The average illness will take your critical resource out for two weeks, but might be as long as three.
Another fun question is when should we start thinking about the rate of illness in our planning process? Here’s a few things that came to mind for me:
If you’re a remote company you should expect that any and all gatherings you run will trigger a wave of sick days. Anecdotally from my time at Daybreak, we would see roughly 25 to 30% of our team take sick time in the following two weeks. Admittedly, this was during ‘22 and ‘23.
Illness rates double in January according to the Bureau of labor Statistics, so you should expect to see impact in that month for any in-flight projects.
On any project with more than ten people lasting more than ten calendar days you’re flirting with a greater than 50% chance of an illness and if Odgerel Chimed-Ochir et-al are to be believed, one illness will cost you ~6 calendar-person days or about twelve percent of your total budget!
Amusingly, startups probably don’t need to care too much about these numbers because the impacts are relatively small compared to other frictions in the business.
As part of writing this I threw together a calculator, which you’re welcome to snag a copy of in case it’s helpful to you.
Bureau of Labor Statistics, U.S. Department of Labor, The Economics Daily, 7.8 million workers had an illness-related work absence in January 2022 at https://www.bls.gov/opub/ted/2022/7-8-million-workers-had-an-illness-related-work-absence-in-january-2022.htm (visited April 17, 2024). (Isn’t it. cool how they give you citations ready to go? So helpful! Good government.)
https://www.linkedin.com/pulse/health-related-work-absence-2023-we-entering-new-era-fred-schott-i2f2e/
https://www.cdc.gov/ncird/rhinoviruses-common-cold.html
https://www.mayoclinic.org/diseases-conditions/common-cold/symptoms-causes/syc-20351605
https://www.hopkinsmedicine.org/health/conditions-and-diseases/common-cold
https://journals.lww.com/joem/fulltext/2019/08000/potential_work_time_lost_due_to_sickness_absence.9.aspx