Wharton professor Gregory P. Nini and I just authored this new paper showing that more than two million additional people would have voted in those primaries had they thought the results would be counted.
Among the proposed alternatives for seating the delegates from Florida and Michigan is to use the results of the primaries that already happened, based on the argument that doing so would avoid disenfranchising the 1.7 million Floridians and 600,000 Michiganders who already voted. However, doing so would disenfranchise many people from FL and MI who did not vote in the earlier primaries because they did not expect their delegates would be seated at the convention. Based on a statistical comparison with turnout in other states' primaries, it appears that roughly two million more people would have voted in FL and MI had they expected their delegates would be seated.
Download the full study here.