independent monetary areas. Business techniques and forms of business organisation employed during this time included early contracts, bills of exchange, long-distance international trade, early forms of partnership (mufawada) such as limited partnerships (mudaraba) and early forms of credit, debt, profit, loss, capital (al-mal), capital accumulation (nama al-mal), circulating capital, capital expenditure, revenue, cheques, promissory notes, trusts (waqf), startup companies, savings accounts, transactional accounts, pawning, loaning, exchange rates, bankers, money changers, ledgers, deposits, assignments, the double-entry bookkeeping system, and lawsuits. Organisational enterprises similar to corporations independent from the state also existed in the medieval Islamic world. Many of these concepts were adopted and further advanced in medieval Europe from the 13th century onwards. Early Islamic law included collection of Zakat (charity), one of the Five Pillars of Islam, since the time of the first Islamic State, established by Allah's Messenger at Medina. The taxes (including Zakat and Jizya) collected in the treasury (Bayt al-mal) of an Islamic government were used to provide income for the needy, including the poor, elderly, orphans, widows and the disabled. During the caliphate of Abu Bakr, a number of the Arab tribes, who had accepted Islam at the hand of The Prophet Muhammad, rebelled and refused to continue to pay the Zakat, leading to the Ridda Wars. Caliph Umar added to the duties of the state an allowance, paid on behalf of every man woman and child, starting at birth, creating the world's first state run social welfare program. Maya Shatzmiller states that the demographic behaviour of medieval Islamic society varied in some significant respects from other agricultural societies. Nomadic groups within places like the deserts of Egypt and Morocco maintained high birth rates compared to rural and urban populations, though periods of extremely high nomadic birth rates seem to have occurred in occasional "surges" rather than on a continuous basis. Individuals living in large cities had much lower birth rates, possibly due to the use of birth control methods and political or economic instability. This led to population declines in some regions. While several studies have shown that Islamic scholars enjoyed a life expectancy of 59–75 years between the eleventh and thirteenth centuries, the overall life expectancy of men in the same societies was lower. Factoring in infant mortality, Lawrence Conrad estimates the average lifespan in the early Islamic caliphate to be above 35 years for the general population, compared to around 40 years for