the OECD, Israel is also ranked 1st in the world in expenditure on Research and Development (R&D) as a percentage of GDP. Intel and Microsoft built their first overseas research and development centers in Israel, and other high-tech multi-national corporations, such as IBM, Cisco Systems, and Motorola, have opened facilities in the country. In July 2007, U.S. billionaire Warren Buffett's Berkshire Hathaway bought an Israeli company Iscar, its first non-U.S. acquisition, for $4 billion. Since the 1970s, Israel has received military aid from the United States, as well as economic assistance in the form of loan guarantees, which now account for roughly half of Israel's external debt. Israel has one of the lowest external debts in the developed world, and is a net lender in terms of net external debt (the total value of assets vs. liabilities in debt instruments owed abroad), which as of 2011 stood at a surplus of US$58.7 billion.
Days of working time in Israel are Sunday through Thursday (for 5 a days 'week'), or Friday (for 6 a days 'week'). In observance of Shabbat, in places where Friday is a work day and the majority of population is Jewish, Friday is a "short day", usually lasting till 14:00 in the winter, or 16:00 in the summer. Several proposals have been raised to adjust the work week with the majority of the world, and make Sunday a non-working day, while extending working time of other days, and/or replacing Friday with Sunday as a work day