The baseline of 0% versus 4% is about fed funds rate, not inflation. The lowest (baseline) rate prior to Reagan was about 4%. Have to go back before 1965 to have lower rates.
Prior to the current administration, the rate was zero (baseline) and had been effectively zero. Had to go back to 2008 to find rates consistently over 1%.
The baseline is one point of figuring the delta between current norms and current rate. If you just use the rate the year immediately prior, it was 13.35% in 1980. It went up to over 16% in 1981, but then fell to 7.6% by 1988. So, rates were lower under Reagan than they were before him by about 6 percentage points. 4% was just me being generous to Carter in the comparison. The point in all of this is that people felt a real positive change versus their 'normal' under Reagan as rates dropped. Rates have increased recently and the normal baseline from which regular people are judging is the zero percent. While the rates may be lower today 5.1% vs 7.6%, the real change for people is an increase of 5.1% versus a decrease of about 6%. That is huge in terms of consumer confidence. Inflation just adds to the problem because they know that prices are way up and the 3% spin is a joke. It has only been that low a few months, not a full year.