You can’t use a system that records kills to establish how many are not killed. Killboard will only show you how many were ganked, or were destroyed by NPCs. There’s no data on how many were mining overall…or what portion of miners were ganked on any day. BUT…there is a slight inference one can draw. The number of Ventures ganked every day in highsec is generally the same as the number of Ventures destroyed by NPCs. That suggests Venture ganking is not really a huge issue.
Some surprising stats…
HIghsec systems 1192
Lowsec systems 688
Nullsec systems 3321
Wormholes 2604