"An effective tax rate on dividends of 70%-is"
That's not different from paying VAT or any sale tax, and even property taxes, with an income which was already taxed, is even worse because it's the same entity.
Companies can still invest their profits, to create more value and jobs, and that's usually less taxed. Too much incentives to dividends may lead to shareholders forcing the company to actually invest less and pay workers less. Remember also paying dividends usually decrease the shares value.
Biting the hand that feeds IT
