看清楚，这里有人引用的“献血中心数目”blood donation centers“!!! 不是卖血者人数！回帖好多人误解了！发帖者是不是有意误导？
2019 美国共有730万献血者。信息来源于
U.S. Blood Donation Statistics and Public Messaging Guide
（Q2.2: How many individuals donate blood annually in the U.S.?
There were approximately 7.3 million donors in 2019.9, 10* *Includes all categories of donation and only successful donations.）
看清了是”donations“！