"Atemi accounts for 99% of aikido." was a remark once uttered by the Founder." This is from Saito Sensei's Traditional Aikido, Vol 4. The quote is given without much context, and there is no indication of the timeline.
There is much confusion about this, as most of our training does not explicitly involve striking. Aikido is not a mostly striking art as defined by the Western mind. I have known students who talk about taking karate or krav maga classes to make their aikido better; to recover this "99% atemi aikido."
There is only one aikido student of Morihei Ueshiba who clearly set up a definition and teaching method of aikido atemi waza that I am aware of (lots of teachers who move with strikes in their techniques, not quite the same thing as what I am talking about).
This is Shomenate, the first movement of Tomiki Aikido's Junana Hon kata, first appearing in the early 1960s. Shomenate is also first movement in the the earlier kata version, the 15 basic techniques developed in the early 1950s - years before any obvious friction between Mr Tomiki and the Aikikai.
The first five movements of Junana Hon kata are named "atemi waza." (And the first three in the 15). When O Sensei said 99% of aikido is atemi, there was a well categorized and developed set of movements called atemi waza codified by one of his students. The simple atemiwaza sets are ubiquitous, indeed appearing often explicitly or implicitly in the movements and techniques of other schools of aikido. They just aren't called atemi by everyone.
Many basic techniques I learned certainly contain this Shomenate posture, if only for a split second. Uchi Kaitenage depends on this for a split second in time, so do most koshinage I was taught. Yokomenuchi Shihonage and Yokomenuchi Iriminage start with this movement. How did I learn Tenchinage and Kokyu-Doza? "Hold on to my wrist, or you're getting my palm in your face." Palm In Face is what I called Shomenate for years.
I was told many times, "If you step into your uke's center and open them up, put a hand in their face." This could be a strike, or a distraction, or just obscuring uke's vision while something else happened. I wasn't given a name for it, nor did I practice it much in isolation. The movement itself is called atemi waza by Tomiki aikido, not the actual contact only. The omnipresent threat of Shomenate in Tenchinage and the actual technique Shomenate are still about Shomenate in my opinion.
Tomiki did not stop with defining atemi as a posture. He was also clear about atemi's purpose: "Although the atemi-waza and kansetsu-waza can be viewed as techniques that can inflict a severe injury on an opponent, if we study the principles of the martial arts well, we realize that they are exquisite techniques for toppling (taosu) or controlling (osaeru) an opponent without necessarily harming him." On Modern Jujutsu by Kenji Tomiki is fully available online at Judoinfo.com.
Combine this statement with Gozo Shioda's explanation of atemi in Aikido Shugyo, "In Aikido, atemi is not limited to punching or kicking. Any part of the body can become a weapon for executing atemi. Some of you may have seen me in demonstrations use my back to repel an opponent rushing at me, or my shoulder to send my opponent flying as we pass each other. The reason these techniques work is that the contact point in itself becomes the atemi."
Neither Shioda nor Tomiki defined aikido atemi as boxing style striking. Atemi was the throw itself. As any body surface making contact can be an atemi, and atemi is used to topple an opponent or control an opponent - then indeed atemi defined this way is the vast majority of aikido. This is absolutely not the same as saying jabs, hooks, and upper cuts are 99% of aikido!
Aikido is said to have changed post war. From two of the prewar greats to a giant of the post-war era, Morihiro Saito's book, Takemuso Aiki: Kokyunage Vol 4 contains this in the foreword: "Kokyunage are the most numerous and important techniques in aikido, hence my decision to devote an entire volume to this subject. If Kokyunage techniques were to be removed from the art, it would no longer be worthy of being called aikido."
The text alone makes it sound like Saito Sensei has disagreed with O Sensei, or said something different, or offered a counterpoint to atemi being the most prevalent techniques. However, demonstrated here by Hitohiro Saito in Takemuso Aiki: Kokyunage, this is a Kokyunage (pg 141):
Gozo Shioda's Aikido Shugyo on atemi: "...my teacher Morihei Ueshiba sensei always had stated that in real fighting occasions 70% of aikido is atemi, and 30% is throwing..."
Why was Shioda's estimate of the prevalence of atemi 29% less than other estimates? Was he saying something different? Maybe not. For one thing, this movement wasn't called atemiwaza but instead was called Sokumen Iriminage. Morihei Ueshiba is on the left, Shioda on the right.
This movement is the third atemiwaza technique in Tomiki's Junana Hon kata, called Gyaku Gamae Ate:
The woman demonstrating is one of Mr Tomiki's students, Dr Lee ah Loi. The palm down is distinctively Tomiki lineage, but the palm up Aikikai style is regarded as a variation. Certainly I was told by Aikikai teachers that the applied movement was an elbow in the throat.
Morihiro Saito in Takemusi Aiki: Kokyunage, pg 153. Hitohiro Saito is demonstrating a kokyunage again. Kokyunage is indeed super prevalent in aikido as Saito defined it - it's just not clearly different from Atemi waza to me, except in name.
As always check out Mokuren Dojo's website and Kaze Uta Budokai's YouTube channel for all things Tomiki, and Stanley Pranin is a never ending resource on Iwama Aikido (but really all Aikido).