Oh how I envy you! We're still slowly getting a reporting culture in place and it's not the easiest thing to establish a good flow of reliable information so you can action the near misses, let alone actually produce useful internal statistics! That said, I'd be inclined to include near misses either within the main chart or in its own with a catch-all block for accidents in order to try an compare the relationship between near misses and accidents. In principal, you should see some correlation between both the reporting (i.e. more incidents of both "types" being reported and, in an ideal world, less accidents occurring as more near misses are reported (assuming, of course, that remedial measures are also being brought in to prevent repetition of the near misses!).

I'm not sure I would want to put it all into a pie chart, as there should be a lot more near miss / hit reports than actual accidents, so the accidents will be squeezed up making them just look less. A Pie chart is always a big round circle, it is therefore harder I think to see reductions. You could show it all together with a line chart (or combination line and stacked bar), that way as you reduce from better controls the near miss / hits, it should also show a reduction in accidents, and so the value of collecting this data. In theory at least, but you have to try don't you. I once had half a jam sandwich in the near miss reporting box! But it was not signed, so I didn't investigate further. Best of luck. Chris