Maybe no such statistics can be obtained from the custom pcb marketplace, because different manufacturers can establish various sales channels. This should not be a key when you consider whether to do the business. As a buyer, you're expected to do research to the local marketplace to figure out the demand. You may have design or own product idea. Then OEM/ODM should be found.
Rigao Electronics is a professional expert in producing pcba service. The Printed Circuit Board is one of the main products of Rigao. The product stands out for its durability. Adopting high-performance materials, its circuit board is protected from shocks, vibrations, abrasion, and harsh weather elements. Rigao is a professional company specializing in production and sales of pcb assembly.
Rigao has been bearing the notion of ethics management in the mind. Ask!