Looking at the handy Inflation Calculator on the Consumer Price Index website, $19,000 per capita in 1980 dollars would be equal to $40836.20 today. Instead, they have about $7,300 according to your article. For the nation as a whole, had their $133 billion in 1980 simply kept up with inflation, it'd be $285.85 billion instead of the $138.8 billion you calculated. That's a substancial decline in real dollars. And remember, these are US inflation numbers. I have no idea what the inflation numbers would be in Saudi Arabia but this does give a view into the drop in their purchasing power.