The Nikkei gap fills less, but only inside the dayNikkei (USD) Futures (Dec 2026)CME:NKDZ2026PerfiltradeThe opening gap does not behave the same way in every index future, and the Nikkei is the clearest case. Measured the same way on both contracts: gap from the prior regular-session close to today's open, filled if price trades back to that close within the same regular session. In the Nikkei future, gaps up fill 40.9 percent of the time across 4,094 sessions since 2010. In the S and P 500 e-mini, 58.1 percent across 4,104 sessions. Seventeen points apart on the same measurement. Then the weekend gap, from Friday's close to Sunday's open, counted as filled if price returns to that close during the week. Nikkei: 84.9 percent. S and P 500 e-mini: 83.1 percent. The difference disappears. What this suggests: the Nikkei's gap is not harder to fill, it just needs more than one US session to do it. Whether that holds going forward is another question; this is a count of what happened, not a forecast. What it does not say: nothing about direction, nothing about when inside the session the fill happens, and nothing about any single day. Measured on exchange data, 2010 to 2026. The indicator on this chart is open source and published on my profile.