Fast forward to now, and a deflationary period and I learn, embarrassingly late, that Uncle Sam actually had a different, slightly more nuanced, definition of "fixed rate" (emphasis mine).
The fixed rate will always be greater than or equal to 0.00%. However, the fixed rate is not a guaranteed minimum rate; the composite rate could possibly be less than the fixed rate in deflationary situations.So, it's fixed, kinda, but if the economy tanks, they let the "adjusted" component of the rate eat away the supposed "fixed" component, making it - by my lowly definition - not so fixed after all. I suspect I'm not alone in learning this nuance, as this is apparently the first deflationary period every experienced since the inception of the I-Bond.
Equally unsettling is that the rate *could* conceivable be pushed below 0.0% such that it actually eats away at any interest earned over the period too! So I should in fact be grateful that Uncle Sam has provided such a great regulation that in the words of my helpful customer service rep...
... regulations allow us to adjust the composite rate [back up] to 0% to prevent the investor from losing any interest earned.... that's good... I guess... but with these terms, I think I'll look for other avenues and leave financing our national debt to the Chinese.