I seem to recall reading a text on pre-Tokugawa Japanese warfare where they quoted specific numbers, but I haven't been able to find it in years (to the point I now wonder if I just imagined it).
I'd be particularly interested in any numbers on causes of death both in the field, and in a siege.
If anyone has numbers on arrows fired versus casualties caused, that would be interesting too.
For Japan, Friday [1] discusses some studies of battle reports. The causes of wounds as percentages from the three studies Friday summarises are:
Conlan: arrows 73%, swords 25%, spears under 2%
Suzuki: arrows 87%, swords or naginata 8%, rocks 3%, spears 1%
Shakado: arrows 82%
One of these studies, or Friday's summary of them, is probably the one you were thinking of. If anybody else knows of any similar data for outside Japan, please post the data or references - this would be very interesting to compare.
References:
To add to /u/wotan_weevil, those numbers are compiled from surviving petitions for rewards in which one notes down the casualties suffered in his units. Suzuki breaks down his analysis by era. Since Friday deals with late-Heian Kamakura, I'm going to guess that's the era he quoted.
Conlan's total for the entire NanbokuchÅ (percentage already cited by /u/wotan_weevil) comes to 523 arrow wounds, 178 blade wounds, 15 spear wounds, and 5 rock wounds.
Suzuki's data for the Sengoku (Onin to Shimabara) is 604 arrows (41.3%), 286 guns (19.6%), 261 yari (17.9%), 150 rocks/tiles (10.3%), 56 sword (3.8%), 35 naginata (2.4%), and 69 multiple sources (4.7%). With a note that guns were not introduced until halfway into the Sengoku, and if only count post-introduction, gun takes 44%.
The casualties reported in the battle report by Kikkawa clan for the clan's assault on Tsu Castle in 1600 comes to 143 gun wounds, 82 yari wounds, 36 arrow wounds, and 1 blade wound.