Webster (3): decreasing in rate as the base increases (a regressive tax)
Webster (4b): increasing in rate as the base increases (a progressive tax)
moneymarketing.co.uk
Tony Wickenden (November 13, 2009). "The 60% tax trap". Money Marketing.
nationalreview.com
Barro, Josh (March 25, 2010). "Alcohol Taxes are Strongly Regressive". National Review Online. خطای یادکرد: برچسب <ref> نامعتبر؛ نام «nationalreview.com» چندین بار با محتوای متفاوت تعریف شده است. (صفحهٔ راهنما را مطالعه کنید.).
reference.com
dictionary.reference.com
Dictionary.com (3). (of tax) decreasing proportionately with an increase in the tax base.