Experimental Constraints on Polarizability Corrections to Hydrogen Hyperfine Structure

We present a state-of-the-art evaluation of the polarizability corrections---the inelastic nucleon corrections---to the hydrogen ground-state hyperfine splitting using analytic fits to the most recent data. We find a value Δₚₒₗ=1.3±0.3 ppm. This is 1--2 ppm smaller than the value of Δₚₒₗ deduced using hyperfine splitting data and elastic nucleon corrections obtained from modern form factor fits.