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We present an up-to-date compilation of published Hubble constant (H₀) measurements that are independent of the CMB sound horizon scale. This compilation is split in two distinct groups: A. Distance Ladder Measurements sample comprising of 20 recent measurements, primarily from the past four years, utilizing various rung 2 calibrators and rung 3 cosmic distance indicators. B. One-Step Measurements sample including 33 measurements of H₀ that are independent of both the CMB sound horizon scale and the distance ladder approach. These 33 measurements are derived from diverse probes such as Cosmic Chronometers, gamma-ray attenuation, strong lensing, megamasers etc. Statistical analysis reveals a significant distinction between the two samples. The distance ladder-based sample yields a best fit H₀ = 72. 8 0. 5 km s^-1 Mpc^-1 with ²/dof=0. 51 indicating some correlations. The one-step measurements result in H₀ = 69. 0 0. 48 km s^-1 Mpc^-1 with ²/dof=1. 37 indicating some internal tension. If two outlier measurements are removed (TDCOSMO. I-2019 known to have systematics and MCP-2020) the best fit of the one step sample reduces to H₀ = 68. 3 0. 5 km s^-1 Mpc^-1 with ²/dof=0. 95, fully self-consistent and consistent with sound horizon based measurements. A Kolmogorov-Smirnov test yields a p-value of 0. 0001 suggesting that the two samples are fundamentally distinct, with a probability of less than 0. 01\% that they are drawn from the same underlying distribution. These findings suggest that the core of the Hubble tension lies not between early and late-time measurements, but between distance ladder measurements and all other H₀ determinations. This discrepancy points to either a systematic effect influencing all distance ladder measurements or a fundamental physics anomaly affecting at least one rung of the distance ladder.
Leandros Perivolaropoulos (Tue,) studied this question.