In nuclear magnetic resonance (NMR), the bulk magnetization of a sample is commonly assumed to be proportional to spin polarization, with each spin of the same type contributing equally to the measured signal. Herein, the high-field theorem for general spin-I systems (where I is the spin quantum number): the total measurable NMR signal remains unaffected by the grouping of spins into equivalent units (e.g., molecules) is proved, provided the system is at thermodynamic equilibrium in the high field limit (