For UV-Vis, the population ratio between the ground and excited state is 1*1042, which means that essentially 100% of molecules will be in the ground state. However, for NMR, the population ratio between the levels is 1.000064, which means that the lower level (α) has only a tiny population excess (50.0016%). To visualize this, let’s assume we have one million ‘species’ in NMR (spins); there would be 500,016 species in the α state and 499,984 in the β state. However, in UV-Vis, we would have essentially 1,000,000 species in the ground state and 0 in the excited state. The population excess for NMR is 32, while in UV-Vis is 1,000,000! This difference in population is the source of the sensitivity, which explains why NMR has inherently low sensitivity compared to other analytical techniques such as UV-Vis.