Estimated number of PBD was obtained by calculating the percentage of PBDs among the whole population(its 95%CL) and population of every stratum.

• 用各层人口数分别乘以该层人群中献血员百分比及其95%25可信区间；计算、汇总；获取目标人群基数。结果4个县21.；8%25(93/1891)的行政村有既往有偿献血员；且呈集中分布;