A decade ago, amid much controversy, I persuaded the Australian government to cut the capital gains tax rate in half.
Stephen Kirchner, an economist from Australia's leading think tank, the Center for Independent Studies, reviewed the results last November.
This a brief summary:
The introduction of capital gains tax discounts for individuals and funds as part of the 1999 Ralph business tax reforms has received a lot of bad press, but much of this commentary is ill-informed. . . .
Those who called for reform of Australia’s capital gains tax regime 10 years ago argued that the Ralph reforms would likely raise more revenue because of the increased incentive they provided for taxpayers to realise capital gains that would otherwise go untaxed. Supply-side economist Alan Reynolds predicted that the reforms would raise twice as much revenue in the long run. He was right. The capital gains tax share of Commonwealth tax revenue nearly doubled between the introduction of the Ralph reforms and 2006–07. In absolute terms, CGT revenue rose from $4.6 billion in 1998–99 to $17.3 billion in 2006–07. CGT revenue growth has been strongest among individuals, who received the larger discount of 50%, followed by funds, which received a 33% discount. The slowest CGT revenue growth has been from companies, which received no discount.
The data suggest that the Ralph CGT reforms have resulted in more tax revenue through increased realisations of capital gains. They have thus strengthened rather than weakened the ability of the tax system to serve equity objectives. The Ralph reforms demonstrate the basic supply-side insight that lower effective tax rates lead to faster growth in the tax base and tax revenue.