The mental gymnastics involved in having a high security clearance.

Why not? Provide your own numbers as an estimate.

You can get a clearance at 18, and people live into their 70s and 80s pretty regularly. The 4.2 million with a clearance are not the same ones that had a clearance 10, 20, 30, 40, 50, 60 etc. years ago.

We had a draft until the early 70s. Tens of Millions of people have been through the military system, and this doesn't even count civilian types, contractors, cleaning people, building facility people, secretaries, etc.

The Vietnam war saw about 9 million people in the military for example.

There's about 25 million vets in the U.S. right now.

It's pretty simple math to arrive at number well above the current number. Remember, just because you aren't in the club, doesn't mean it isn't big.

Let's look at what 10% means. There are ~300 million people in the U.S. 10% of that number is 30 million. Let's say that every single man and woman who is currently in the military or has previous served has a clearance (with no overlap). There are about 3 million active and reserve people right now in the military.

25 + 3 = 28 million. Now let's add in non-military government civilians with clearances, the CIA for example is a civilian agency with an estimated 20,000 people, DIA, 16,500, DTRA, 2,000, DOE: ~110,000, NGA 16,000, NRO, 3,000, NSA 20,000 (civilians only, 38,000 total), DHS, 216,000, DOJ, ~112,000, State, ~50,000, etc.

I'm not even including treasury. And we're up to almost 29 million people.

Now how many contractors do you think have Secret clearances?

Lockheed Martin employes over 100,000 people, Northrup Grumman, 120,000, General Dynamics, 91,200, SAIC, 46,000 etc. etc. etc.

And we rapidly go past 1:10.

Now obviously not every single person I've listed has (or has had) a Secret clearance. But until you start shaving off huge percentages out of each organization you're still between 1:10 and 1:15.

If you disagree with these numbers, the onus is on your to provide better ones.

You actually can't handle classified data, or derive something from classified data, that doesn't automatically classify the derived work (a report, or some such) at at least the same level. To not do that risks releasing the information and you can actually end up in prison over it, or at the very least lose your job.

So in 99% of the cases it's not like you make a decision to "classify" something. It is by its nature classified.

Think of it this way. You have a friend that tells you via email a secret. This secret can only be known between you and your friend. For example, you are arranging a surprise party for a third friend.

Using this knowledge it is your job to get a birthday cake that has the person's name and age (and a decoration) on it. But the only baker in town is also friends with the birthday friend. You don't want to risk the baker leaking the surprise of the cake to your friend. So you decide to buy a blank cake, and decorate it yourself.

This cake is also classified at the same level of the original information (Classified//only between you and your friend). Because it is derived from the knowledge of the birthday party email).

Now your friend prints off decorations with some party specific information, say a sign or some streamers or something. Those are also classified at the same level.

Suppose there are some other odds and ends that are a result of this email and the party plans. Say a "making of video" for the party etc.

Now let's say you also hire a clown for the party. You only provide the clown the time and place to come and perform, not any other details. Because the clown isn't in on the original secret, the arrangements for the clown and the various transaction documents pertaining to it are at a lower classification level. You might still not want the birthday friend to know that somebody he knows hired a clown on his birthday (a convenient coincidence) so you swear the clown to secrecy.

Even if it gets out and the birthday friend asks the clown directly, the clown has plausible dependability and doesn't know why he was hired, only that he was. So it's not good that your friend finds out, but it doesn't entirely screw up the surprise.

I'm stretching the analogy a bit, but hopefully that makes it clear how knowledge of single piece of information (the email that established the surprise party) can end up producing so many classified documents and how that process happens.

If your understanding of the military comes from 1960's television sitcoms, you're not qualified to discuss this subject.