The 20% figure has no value out of context, since what matters is their share of income, not their share of the population. Happily the WSJ article does include

The 20% figure has no value out of context, since what matters is their share of income, not their share of the population. Happily the WSJ article does include that figure: the top 20% earn 51.3% of the income. It also goes on to say that "The share of tax paid by the top 20% of Americans also changes when such social-insurance levies [Social Security and Medicare] are included: It drops from more than 80% of income taxes to about 67% of all federal taxes."