Economically, Japan's GDP per capita (measured in 2010 US$) was 39,240 in 1991 and grew to 49,000 in 2019, a 25% increase. Yes, it's slower growth than before, but slow growth is still growth, not stagnation. For comparison, New Zealand was at 38,345 in 2019: https://data.worldbank.org/indicator/NY.GDP.PCAP.KD?end=2020... (also threw in the graph for South Korea)

During that time the USD has suffered around 88% inflation measures by CPI, so in real terms that implies they're going backwards.

When my parents went to Japan in the eighties they were shocked that coffee in Tokyo was 4 times as expensive as in Germany. When I visited in 2016 I was similarly shocked that a vending machine Coca Cola costs half of what it costs in Germany. Japan's deflation has led the country to be very affordable.

That's inflation in US prices. It may not be transferrable to another country, where various things cost more/less, and rise/fall differently through the years.

> stagnating

That's a nice way to put it, it's been actually decreasing clearly over time since 1989, with ups and downs on the way: https://mebfaber.com/wp-content/uploads/2009/12/japan.jpg

What is the y axis?

That chart is a crude snapshot of the Nikkei 225 from 1990 to 2009. Since then it's rebounded by quite a bit although it's still quite a bit under its Dec 1989 peak. But of course a stock market index isn't the full economy, so I would disagree that this chart by itself constitutes proof that Japan is stagnating.

Chart source: https://mebfaber.com/2009/12/20/japan-the-us-and-the-lost-de...

It has been in stagnation since the 80s: https://en.wikipedia.org/wiki/Lost_Decades_(Japan)