In open innovation companies open up their own innovation processes and integrate knowledge from external stakeholders like customers, lead users or competitors. This is called the outside-in process (inbound open innovation). On the other hand, companies try to externalize knowledge (innovations, products, licenses) which is currently not used. This is called the inside-out process (outbound open innovation).
The WU Vienna carried out a study on open innovation of which an abstract can be found here.
An OECD Working Paper (Open Innovation in a Global Perspective - What do Existing Data Tell Us?) on Open Innovation can be studied for further reference. The paper for examlple presents different indicators using existing data on R&D investments, innovation survey data, patent data and data on licensing, illustrating the increasing importance and the different characteristics of open innovation across companies, industries and countries.