An analysis from the Urban Institute provides state-by-state estimates of the impact on insurance coverage, premiums, and mandate penalty revenues if the states were to adopt individual mandates. If all states did so, the number of uninsured would be lower by 3.9 million individuals in 2019 and by 7.5 million in 2022. On average, marketplace premiums would be 11.8% lower in 2019.
The report can be obtained at https://www.urban.org/sites/default/files/publication/98805/2001925_state_based_individual_mandates_2.pdf.