When people in New Jersey argue about taxes, those opposed to higher taxes warn that the 2004 income tax increases accelerated outmigration of high-income people in New Jersey.
Here's an example of an outmigration warning from January 21, 2019 by Assemblymembers Kevin Rooney and Christopher Phillips.
After income taxes were increased in 2004 on people earning over $500,000, New Jersey lost $18 billion of gross income over the next nine years. Then the problem got worse. In 2013, 35 percent of the people who moved out earned over $150,000, just three years later it was 45 percent. High-income residents decide to reside elsewhere because they are taxed more than in any other state.
I've seen numerous attempts by the New Jersey Policy Perspective and similar liberal groups to debunk this, but the claim that the 2004 tax increase worsened income outmigration is correct.
The New Jersey Policy Perspective claims that income can never be taken out of a state because income is tied to an employer or client base, but 25% of NJ's income is non-wage income that is transferable and sometimes salary income is transferable if someone works from home, someone's employer relocates, or if someone moves to another state and keeps the NJ job.