In 1990 the top three carmakers in Detroit had a market capitalisation of $36 billion and 1.2m employees. In 2014 the top three firms in Silicon Valley, with a market capitalisation of over $1 trillion, had only 137,000 employees.
Ford has four times the debt that it has equity. Enterprise value (debt plus equity) is a better measure.
The other thing that gets lost is jobs in the supply chain.
This may not change the end conclusion, but the existing methodology is flawed.