The article says
An orthodox relief program would pay the jobless head of a family, say, $60 a week. If he then started to earn something, he would be paid simply the difference between that amount and $60. Under the NIT principle a man who was earning nothing would also receive a relief payment of $60 a week. But if he then earned $30 a week on his own he would still get a $45 payment (reduced by only $1 for every $2 earnings), bringing his total income to $75 a week.
I am not an economist. Infact this was the first post where I ever heard of negative income tax. However, I feel that the numbers in the examples just don't add up.
According to me under the NIT principle if he earned $30 a week on his own he would still get a $15 (half of the difference) payment from the government. So his total income would be $45 and not $75.
So there is no anamoly. Anytime a person earns more than $60 he gets nothing from the government. Anytime he earns less than $60 he would be just that much close to $60. So earning $58 a month would get him $1 from the government for a total salary of $59.