Investment income is flat taxed.
And inheritance taxes, which are very high in France.
If you want to increase taxes, consider taxing income more and capital gains at a progressive rate. Although I haven't seen good data on effects of say a 70% capital gain tax, might hurt th,e economy. I did some reading on this subject last month and the sweetspot was around 20% to 35% on that classification of income.
Do you want to take people's wealth and cap it? IE, nobody is allowed more than $5 million? What are you advocating for instead?
For example, how do you tax a private business? In Spain, for example, it is a big carve-out, which leads to people never selling a company, which hurts their economy as you have tons of zombie companies. Or what people do is they take their money and buy apartments and rent them out on Airbnb, wrap them in a business, and get around the wealth tax.
The most effective way to tax wealth is to tax income, capital gains, and inheritance effectively.
But, lets say you can wave a magic wand and tax wealth (France already taxes real estate with a wealth tax + property tax).
What would a 2% yearly wealth tax raise? Maybe 15 to 25 billion a year in France, so it does nothing.
Would this actually cover France's deficit?
And people will just move, or move it around.
France already has a wealth tax on real estate + property taxes.
America's $6.75tn budget [1] would blow through our $140tn private wealth in 21 years. Even Norways $0.11tn budget [2] blows through its $1.6tn of private wealth in 14 years.
Perhaps the better metric is deficit as a fraction of private wealth? If that looks unsustainable, the problem is in publicly-held assets and services.
[1] https://fiscaldata.treasury.gov/americas-finance-guide/feder...
In the last 5 years French public debt has grown $750b [1]
Had that growth in wealth been taxed at the rate income was taxed (45%), that would have seen France's debt decrease - even with the covid mess.
[1] https://www.ceicdata.com/en/indicator/france/national-govern...