Morning Mark
Why would the Board members be interested in tiny cuts - unless there is some underlying reason why these are happening?
I don't know what sort of business you work for but you have previously posted about the role of the Principal Contractor, so I guess you are in construction with some risks that pose threat of life changing (or limiting) injuries or illnesses, which could include e.g. falling from height, being struck by a vehicle, breathing in silica dust, exposure to e.g. noise, or being stressed out to the point of suicide.
So, I would be focusing any report to the Board on the things that REALLY matter.
How you classify injuries (and other incidents) is largely up to you, except that you need records of some incidents that meet legally set criteria (i.e. those incidents covered by RIDDOR) and you might want to keep data on incidents that do NOT meet those criteria (as example work-related road traffic incidents that are mostly excluded from UK reporting and record keeping legislation).
Unless you work for a mega sized organisation it is very unlikely that you can detect any statistically significant trends in incidents or incident frequencies in periods of less than years.
So, I would be giving my attention to telling the Board about the positives (leading indicators) and not spending much time boring them with stats that mean nothing, not least since you could create a rod for your own back.
Suppose you track and report all known injuries.
Month 1 - 2
Month 2 - 4
Month 3 - 6
Well, performance in Month 3 is three times as bad as when you started, so the Board might as well give you the sack!!
Except that, perhaps, you are actually getting better intelligence as to what is happening on the ground. The workforce are actually bothering to tell you about that sticking plaster incident that they wouldn't have reported previously.
So, may be performance in Month 3 is actually three times better, not least since the two events in Month 1 were major fractures and you haven't had any of them since.
OK, so you can sort that particularly statistical oddity by splitting your (already small) numbers into categories by severity - but this just makes the statistics even more difficult to analyse by trend.
Month 4 - you have no fatalities.
Month 5 - you have one fatality - so that is an infinite percentage rise in fatals month on month.
Month 6 - you have no fatalities - an infinite improvement month on month. Give yourself a bonus? No - because you also had three RIDDOR recordable Over 3 Day accidents when you had none in Month 5.
If your Board is going to take health and safety seriously and own it as an integral part of their line management function, they need information that helps them make decisions. Rarely will the accident statistics give them such information.