The website [LearnEMC.com](https://learnemc.com/) has a page called [Identifying Current Paths](https://learnemc.com/identifying-current-paths) which contains the following graphics.

![enter image description here](https://i.stack.imgur.com/8P1h1.png)

The graphic on the left shows a coaxial cable arranged in a "U" shape, with a shunt connecting the shield at each end of the U. The graphic on the right shows that at low frequencies, current "prefers" to travel through the shunt, rather than in through the longer coaxial shield. However, at higher frequencies, the current "prefers" to travel through the coaxial shield, rather than through the shunt. That is, the current prefers to travel in oppositely travelling pairs, even though one of the pairs has a shorter alternate path.

The purpose of this graphic is to illustrate a special case of the principle that "current seeks the path of lowest impedance". (Obviously, current doesn't *only* travel through that path, but prefers it. However, this graphic seems relevant to the current discussion regarding [Veritasium's video](https://youtu.be/bHIhgxav9LY) regarding the propagation of electricity. For example, [this question](https://electronics.stackexchange.com/questions/596185/how-long-does-it-take-for-energy-to-propagate-in-a-circuit) and [this question](https://electronics.stackexchange.com/questions/598843/what-is-the-physical-model-for-energy-flow-in-or-around-a-lossless-conductor-dur)

How might one calculate the percentage of current flowing through the shield vs that through the shunt? Would the following procedure work?

1. Ignore the shunt, and calculate (or measure) the impedance of the coaxial cable by itself, then
2. Ignore the shield of the coaxial cable, and calculate (or measure) the (highly irregular) transmission line formed by the coaxial cable's inner conductor, together with the shunt.
3. Assume the ratio of current between the two paths is inversely proportional to the ratio of the two impedances found in 1 and 2?

I am inclined to believe that the shunt has little or no effect on the impedance of the coaxial cable. I have a doubt however, that the impedance found in step 2 is meaningful. After all, the inner conductor is shielded in reality, and that makes me question whether the impedance found in step 2 is at all meaningful.

Is there another method for calculating the current through the shunt as a function of frequency? Perhaps for special cases or special geometries?