Actually, supply side works every time its implemented:
In 1921 the top marginal tax rate was 73%. The Secretary of the Treasury at that time, Andrew Mellon, managed to convice Congress to pass a series of three tax cuts that reduced that top marginal rate to 25% by the year 1926. While the top rate was being reduced by nearly two-thirds, the bottom tax rates were eliminated altogether. Millions of lower income Americans had their income taxes cut or even eliminated. As a result of those tax rate reductions, the US Treasury increased revenues from earners making more than $50,000 by 63%, from $305 million to $498 million in just five years. At the same time, those earning less than $50,000 had their tax liability reduced by 45%.
By the 1960s, the top marginal rate had once again climbed to a confiscatory 91%. Tax cuts enacted by President Kennedy in 1963 and continued by President Johnson through 1965 reduced that top rate from 91% down to 70%, still ridiculously high, by any measure. At the same time, the bottom rate was dropped from 20% down to 14%. The reduced tax rates benefited nearly nearly every taxpayer. The results were much the same as what was experienced in the 1920s.
...
The Reagan tax cuts of the 1980s reduced the top marginal tax rates from 70% all the way down to 33%. As in previous Supply-Side tax cuts, the real taxes paid by wealthy wage earners increased dramatically, even as rates were reduced. As a proportion of overall revenue, high income earners paid a greater proportion as well. The top ten percent of all wage earners paid almost $200 billion in 1988, compared to about $151 billion in 1981. That is an increase of almost 33%. At the same time, the bottom 90% of all taxpayers found their tax liability reduced by nearly 8% from nearly $162 billion in 1981 to just over $149 billion in 1988.
http://www.theminorityreportblog.co..._supply_side_economic_theory_and_why_it_works
