Immediately after agreeing to form a supreme national government, the delegates turned to the Virginia Plan's proposal for proportional representation in Congress. Virginia, Pennsylvania and Massachusetts, the most populous states, were unhappy with the one-vote-per-state rule in the Confederation Congress because they could be outvoted by the smaller states despite representing more than half of the nation's population. Nevertheless, the delegates were divided over the best way to apportion representatives. Quotas of contribution appealed to southern delegates because they would include slave property, but Rufus King of Massachusetts highlighted the impractical side of such a scheme. If the national government did not impose direct taxes (which, for the next century, it rarely did), he noted, representatives could not be assigned. Calculating such quotas would also be difficult due to lack of reliable data. Basing representation on the number of "free inhabitants" was unpopular with delegates from the South, where forty percent of the population was enslaved. In addition, the small states were opposed to any change that decreased their own influence. Delaware's delegation threatened to leave the Convention if proportional representation replaced equal representation, so debate on apportionment was postponed.