The negative income tax combines a guaranteed minimum income with an incentive to work. Below the cutoff point in the example (which was $3,000 in 1968 but would be about $20,000 in 2013 dollars), every dollar earned still increases total income by $1.50. This encourages people to start working and keep finding more work to do, even if the wages they receive for this work are low. It also encourages them to file tax returns and so become part of the visible mainstream workforce.
