Just a hunch, but if the corporations you are looking at are publicly traded, then they probably publish their financial information. You could then trace back the ownership structure up / downward. I've never actually done that, but I assume that could be a source of information.

Thanks Nicolas. We've looked at the 11k fillings (annual financial disclosure for public corporation) and it does not seem to have any useful data to measure that.

There are different methods to calculate the degree of vertical integration.

The official statistical offices use the ratio Value added / Production or sales/turnover. Easy to find the right data, easy to compare sectors. But, you need to discuss some evolution of the products technological progress for each sectors

If you can collect accounting data (enterprises or statistical offfices), you can also calculate the ratio : subcontract purchase or purchase of goods / sales. Here again, you need to manipulate carrefully this indicator if you work on historical data and also, there are some specific traditions (way to interpret the rule) from one sector to another one (and from one country to another one) about the ways to register these data in the accounting system.

Vincent Frigant : Merci beaucoup. Really helpful.