My numbers shift depending on whether one practices the chil sung and yuk ro hyung as well as the basic associated.
Tang Soo Do without Chil Sung, Yuk Ro, and Ho Sin Shul is about 75% Japanese. The comment was made that Hu-ri was innovative and that it was Korean. From my experience Hu-ri is one type of hip movement found in Shotokan and it is emphasized more strongly with all of the techniques in TSD.
With that being said, there has been some direct transfer of technique from Okinawan Karate. Many of the techniques that we practice in TSD are more circular then there Japanese counterparts and this is more reflective of Okinawan practice. Whether this is because of coincidence or direct influence, I am not entirely sure. That said, I'd put the number at 5%.
The Korean component of TSD comprises the addition of several methods of kicking, some terminology and philosophy, and the creation of Ho Sin Shul. Where exactly Ho Sin Shul techniques come from would be a great thread on its own, but I generally see these Korean adaptations of some techniques in Aikijutsu. In the end, I'd put the figure at 20%.
When you add in the new basics, the Chil Sung, and Yuk Ro hyungs, then you see a shift. You see a decrease in the amount of purely Japanese material and an increase in influence from China. The techniques aren't purely Chinese, but they were obviously inspired.
I would say Japanese 60%, Korean 25%, Chinese 10%, and Okinawa 5% if TSD is practiced with the typical Federation SBD syllabus.