You absolutely should do the same spatial inequality analysis in Japan and Italy as well (in fact, this is the norm in Italy's policymaking space due to the doc

You absolutely should do the same spatial inequality analysis in Japan and Italy as well (in fact, this is the norm in Italy's policymaking space due to the documented north-south divide). Heck, this is called out in the Nature article as well if you read TFA. The US (330m), Japan (120m), and Italy (60m) are all large countries, and in the US and Italy's case, extremely federalized with social service delivery responsibilities falling onto subnational governments. And for large developed countries like the US, UK, France, Germany, Italy, Japan, etc their developmental indicators have largely converged at a macro-level (the difference in living standards between countries with a national HDI of 0.900, 0.920, and 0.940 are marginal), but spatial inequality continues to act as a persistent laggard. Outliers matter. This is like statistics/EDA 101. P.S. If you do EDA on Japan versus US from an HDI perspective, you find that the Southern Kanto region (ie. Greater Tokyo) tends to skew Japanese statistics - with a subnational HDI comparable to MA - but the rest of the subnational regions of Japan have HDIs comparable to Tennessee (0.890-0.900) or Florida (0.920-0.930). What this highlights is that public service delivery is stronger in the Greater Tokyo region than the rest of Japan. And this is unsurprisingly a major topic of discussion in Japanese policymaking as well, as the poorer regions have seen a massive youth flight to Tokyo. Same with the less developed regions of the US as well. When you do a similar spatial analysis of the US, you find the Deep South (MS, AL, AR, LA), Appalachia (WV, TN, KY), and MO continuing to lag. You also end up identifying rust belt states like MI and OH starting to lag. The interest thing is, the Deep South and Appalachia didn't seem to lag in the early 1990s compared to the rest of the states, but remained stuck at 1990s levels while other states improved significantly in the 2000s and 2010s, and it was these states that regressed the most in the COVID years (2020-2022) [0]. My running theory is that these states were the kinds of states where low value single factory/industry towns (eg. Textiles) were most prominent, and were the worst hit by a mixture of NAFTA, China Shock, and the Great Recession. This would also explain why GA, NC, and SC didn't see the same laggardness despite being comparable with the rest of the south in the 1990s - Atlanta, Charlotte, RTP, Greenville, and Columbia were industrialized enough in high value industries like automotive and power systems and had significant additional industries like Finance and Tech that allowed them to upskill and diversify. [0] - https://globaldatalab.org/shdi/table/healthindex/USA/?levels=1+4&years=~1992+1991+1990&interpolation=0&extrapolation=0 https://globaldatalab.org/shdi/table/healthindex/USA/?levels...