What is the effect of being president on a person's net worth?
I am most interested in the current president. And any possible reasons.
The President's salary is $400,000 a year. But compared to other things, that's actually chump change.
In recent times, a big economic benefit for some Presidents has been the speaking fees one could command afterwards. Bill and Hillary Clinton apparently received a combined $153 million in speaking fees during the years 2001-15. Obama can earn $400,000 by giving a speech. George W. Bush earns about $175,000 per speech; the lower number may be due to the fact that his speeches were generally in private fora, and he also avoided criticizing Obama. Even Jimmy Carter could earn $50,000 for a speech.
In Trump's case, his net worth, as estimated by Forbes, dropped $400 million last year. The article gives two reasons: a weak New York real estate market, and Trump's Presidency itself. He has been donating his salary to various Federal departments.
Before Trump, Presidents typically put their assets into a blind trust, meaning that other people managed their assets, and the President was in the dark about them. But that would have been difficult for Trump; part of the value of (say) the Trump Tower lies in the fact that it is, in fact, the Trump Tower. If he were to sell it, and it were to become (say) the Gates Tower or the Buffett Tower, it just wouldn't have the same ring, and in the business world, that matters. He has instead elected to have his children run his business, and also has said he won't do any new foreign deals while he is President, and is putting restrictions on US deals. That doesn't remove the ethical issues, but it does reduce them, as doing foreign business deals while President would be far too easy, for all the wrong reasons. The Onion had a cute take on this that probably has a grain of truth.