That’s what you can count on showing up. Calling a CTA 2 days in advance? Count on 33% of your active pvpers (in that time zone) being available. Got an emergency in your home area? About 33% of your folks online will be available/not AFK. I learned this rule from Rico Minali and Sons of 0din WAY back in the day and it’s held true ever since. There’s fluctuations, some people can bring more, some people can bring less. When I make plans and assumptions I figure things based on that number.
The key term in the first calculation is “Active PvPers” a corp or alliance can be seriously weighed down by the number of non-contributing characters and it can make them look just awful. For example; last week I had a couple of guys who had numerous alts in corp from a wormhole we occupied. They didn’t do anything, and since we left the wormhole, most of them just stayed logged out. Some of them still in the wormhole. They inflated our numbers quite a bit but threw off any estimates the alliance might make of our participation. Removing them allows for a more effective estimate of our capabilities as a PvP corp.
These estimates are a key part of strategic planning when it comes to alliance level operations. Knowing what you can do and how much and how long you can sustain these operations is a HUGE part of winning at EvE as time stretches out. Everyone can win the first few fights but staying power comes down to the 33% who keep going. So take a look at your corp membership and ask yourself who you can count on to ship up and undock and who you can’t. Ask yourself what the rest add to the party. Get answers.