to take turns getting pregnant in which case the siblings are only biologically related on the donor side. Sperm banks rarely impose limits on the numbers of second or subsequent siblings. Even where there are limits on the use of sperm by a particular donor to a defined number of families (as in the UK) the actual number of children produced from each donor will often be far greater. Since 2000, donor conceived people have been locating their biological siblings and even their donor through web services such as the Donor Sibling Registry as well as DNA testing services such as Ancestry.com and 23andMe. By using these services, donors can find offspring despite the fact that they may have donated anonymously. Donor payment The majority of donors who donate through a sperm bank receive some form of payment, although this is rarely a significant amount. A review including 29 studies from 9 countries found that the amount of money donors received varied from $10 to €70 per donation or sample. The payments vary from the situation in the United Kingdom where donors are only entitled to their expenses, to the situation with some US sperm banks where a donor receives a set fee for each donation plus an additional amount for each vial stored. At one prominent California sperm bank for example, TSBC, donors receive roughly $50 for each donation which has acceptable motility/survival rates both at donation and at a test-thaw a couple of days later. Because of the requirement for the two-day abstinence period before donation, and geographical factors which usually require the donor to travel, it is not a viable way to earn a significant income. Some private donors may seek remuneration although others donate for altruistic reasons. According to the EU Tissue Directive donors in EU may only receive compensation, which is strictly limited to making good the expenses and inconveniences related to the donation. Equipment to collect, freeze and store sperm is available to the public notably through certain US outlets, and some donors process and store their own sperm which they then sell via the Internet. The selling price of processed and stored sperm is considerably more than the sums received by donors. Treatments with donor sperm are generally expensive and are seldom available free of charge through national health services. Sperm banks often package treatments into e.g. three cycles, and in cases of