The proposal was to introduce a one-time 5% tax on net worth exceeding $1 billion, or about $10 billion.
The referendum was held in conjunction with last week's midterm elections, but the results were not available until Monday, according to the AP.
Critics of the proposal have warned that it could lead extremely wealthy taxpayers to leave the state.
According to the AP, the no side has raised almost ten times more money than the yes side, partly through donations from wealthy individuals. For example, Sergey Brin, co-founder of Google, has spent more than $100 million to defeat the proposal.
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