Membership is usually based on a common bond among members, often through the
workplace or the community. Because of the common bond boundaries, outreach for
individual credit unions is limited, ranging from a hundred to a few thousand members.
从整个句子来分析,应为共同债券,outreach for individual credit unions is limited,讲的是个人信贷,那么个人信贷的基础应该是基于大家共同建立的共同债券,由于共同债券承载的信贷量是有限的,那么由此限制了成员人数。好像银行的存款规模限制了贷款规模是一样的。个人所见,不足请见谅