Each Dalai Lama had two money-lending agencies. Some money coming from "tribute" to the Dalai Lama was lent at an exorbitant rate of interest. According to records in the account books of the two agencies, in 1950 they lent 3,038,581 liang of silver as principal, and collected 303,858 liang in interest. Governments at different levels in Tibet also had many such agencies, and lending money and collecting interest became one of the officials' duties. A survey done in 1959 showed that the three major monasteries, namely Drepung, Sera and Ganden, in Lhasa lent 22,725,822 kg of grain and collected 399,364 kg in interest, and lent 57,105,895 liang of silver and collected 1,402,380 liang in interest. Revenue from usury made up 25 to 30 percent of the total revenue of the three monasteries. Most aristocrats also engaged in usury, with the interest accounting for 15 to 20 percent of their family revenues. Serfs had to borrow money to survive, and more than 90 percent of serf households were in debt. French traveler Alexandre David-Neel wrote in his book Le Vieux Tibet Face à la Chine Nouvelle (Old Tibet Faces New China), "All the farmers in Tibet are serfs saddled with lifelong debts, and it is almost impossible to find any of them who have paid off their debts." Serfs were burdened with new debts, debts passed down from previous generations, debts resulting from joint liability, and debts apportioned among all the serfs. The debts that were passed down from previous generations and could never be repaid even by succeeding generations accounted for one third of the total debts. The grandfather of a serf named Tsering Gonpo in Maizhokunggar County once borrowed 50 ke of grain from the Sera Monastery. In 77 years the three generations of the family had paid more than 3,000 ke of grain in interest, but the serf owner still claimed that Tsering Gonpo owed him 100,000 ke of grain. There was another serf named Tenzin in Dongkar County who borrowed one ke of qingke from his master in 1941. In 1951 he was ordered to pay back 600 ke. Tenzin could not pay off the debt, and had to flee. His wife committed suicide, and his seven-year-old son was taken away to repay the debt by labor.