What the US Treasury department is doing is „active duration management“

By not issuing long-dated treauries as much, institutions like pension funds, etc. are starved from getting these long-dates securities. As they are mandated (and incentivized by their business model) to buy long-dates treasuries still, demand „outpaces“ supply, which drives up prices and yields down (there an inverse relation between price of bonds and their yield).

How to measure/estimate this?

One way to do this is to compare the 10 year treasury yield to the yield for bonds on the agency mortgage market. The latter is low-risk and got the backing of the US government ss well, so these bonds are almost like treasuries.

In bond speak however, they have longer duration and greater convexity, which is why, when you compare these you have to factor in these differences. You can do that by help of a calculation where you make these to comparable by filtering out convexity and duration and when you do this, you still get about a 100 basis point difference which indicates that this is by how much US treasuries are overvalued or their yield is suppressed.