It's interesting to see how the SPY ETF, which represents a significant portion of the US stock market, can be used to measure market trends and volatility. It would be even more useful to have a longer database available for analysis, perhaps going back to 2000, to include multiple market crashes for comparison. I am from Finland and am more insightful about that market. In fact, comparing the performance of Helsinki stock exchange the to that of the US market could provide useful insights and potentially even opportunities. It's also worth noting that Helsinki's stock market, while smaller in size, has seen its own share of ups and downs over the years and could potentially be analyzed in a similar manner. Have you had a chance to follow any other country indices?