The movie showed him become wealthy as a result of Hurricane Carmen, where he was the last shrimp boat standing and expanded.
After that, he had his money invested into a “fruit company” that also shared the same logo of another company created by Steve Jobs. Lets imagine it was that company.
Hurricane Carmen hit in 1974.
Forrest mentioned they had 12 boats “Jenny’s” as a result after that.
From there, it’s figuring out the revenue of the business.
Right now, deckhand shrimp boat operators make on average $41,000 a year.
In 1974 money, that’d be $7,100 a year.
Also, for industry size reference, the Louisiana seafood business is a 2.4 billion dollar a year industry.
For shrimp, there’s an estimated 3,000-5,500 shrimp boats currently in business.
That all being said though, I think the easiest way to create an idea of how much they’d make would just be comparing their revenues to the Bubba Gump Shrimp Company, which started as a franchise/retail brand after the movie.
Which today does 257 million a year in revenue.
Adjusted for inflation, in the 1970s, it’d be making 44.9 million a year in revenue.
From there, seafood is a lower profit margin industry, with a 4% margin, meaning they were making 1.7 million a year.
Split between Forrest and Lt Dan, that revenue $850,000 a year.
4.8 million a year in today’s money.
After that, there’s Apple which IPO’d in 1980.
Lets assume for a moment all of Forrest Gump’s 1980 profits went into Apple.
Apple opened with a market cap of 1.8 billion.
Forrest having $850,000 put into it would own .47% of the company.
Which at that point, Forrest gave 50% of his earnings to Bubba’s mother, putting him to .235% of Apple.
He also donated a large part of it and it’s hard to call how much, but lets go with 60%, due to gross income tax deductions.
That puts Forrest at owning .094% of Apple.
Forrest was pretty humble, so he likely never spent that money and Apple is worth today, 2.68 trillion dollars.
That means Forrest Gump would be worth 2.4 billion today, assuming that was the only time Lt Dan bought Apple stock for him.
Took a few liberties here, but that’s how Forrest Gump the billionaire happens.