what can be the proxy variable for measure of product innovation? My objective is to prove that international trade leads human capital formation which leads to economic growth. I am regressing GDP on multiple variables among which Human capital is one. According to a paper, I've read, new lines of product provide more learning by doing opportunities for workers and hence accumulation of human capital. Since panel data on product innovation is not available, it uses 'first time export' of a commodity as an indicator of product innovation. The source for the data is https://comtrade.un.org/db/
But I don't understand how to identify first time exported commodities.
i need suggestion for what other variables can be used as a proxy for product innovation.
UN COMTRADE has export data by country-product at the HS 6-digit level. What you could do to find out when the product was first exported is to get data for a country's export for product, say, with HS code 123456, from as far back as possible, and see when was the first year that the export of this product is not zero.

I've seen number of patents filed used as a proxy for product innovation in some papers. That might work for your paper as well?