Two currencies, two fates: what 35 years did to the dollar and the yen

Why this matters for your money

Inflation isn't an abstract index — it's the speed at which cash savings decay. An American who kept $10,000 under the mattress in 1990 holds about $4,100 of 1990-era buying power today. A Japanese saver doing the same kept about ¥8,300 of every ¥10,000. Neither outcome is "good" — Japan's near-zero inflation came packaged with decades of near-zero wage growth and the deflationary stagnation of its Lost Decades — but the contrast is the cleanest real-world demonstration that the same act of saving has wildly different consequences depending on the currency it happens in.

It also reframes investment returns. A US portfolio had to grow ~150% over the period just to stand still in real terms; a Japanese one needed ~20%. "Money held its value" and "money grew" are different claims, and the gap between them is exactly what this chart measures.

Method

US series: Bureau of Labor Statistics CPI-U, annual averages, rebased to 1990 = 100. Japan series: Statistics Bureau of Japan CPI (2020 = 100 base), rebased to 1990 = 100. Figures are approximate annual averages rounded for readability; both series are refreshed each January when full-year data lands. Run your own years through the inflation calculator.