1. From the wiki article, France gets 0.3% on financial transactions
France
On 1 August 2012, France introduced a financial transaction tax in French tax regulation pursuant to Article 5 of the French Amended Finance Bill of 14 March 2012. Two other taxes applicable to financial transactions were also introduced, including a tax on
high-frequency trading, (Article 235 ter ZD bis of the FTC); and a tax on naked sovereign credit default swaps (Article 235 ter ZD ter of the FTC). The FTT levies a 0.2% tax on stock purchases of French publicly traded companies with a market value over €1 billion. The scheme does not include debt securities, except convertible and exchangeable bonds, which are included but benefit from a dedicated exemption to the FTT.
[49] According to French president
Francois Hollande the tax will generate €170 million in additional revenue for 2012 and another €500 million in 2013.
[50] France is the first European country to impose a transaction tax on share purchases.
[51] From 2 January 2017 settlement date the rate increased to 0.3%.
[52]
2. According to the Federal Reserve the US gets about $5T a year in financial transactions,so a 3% FTT would raise $150b a year
see page 9, I'm estimating $5T annually as a reasonable number of US financial transaction value. That could be seriously undervalued based on multiple buys & sells in a year.
Bottom line: adjust the rate to get the desired income.