survey of empirical immigration studies in 1995, they authors found that while some cross-sectional studies showed a slight decrease in domestic worker wages as a result of immigration, the effect was only slight, and not particularly detrimental. Pischke and Velling came to similar conclusions in a cross-sectional German immigration study. Studies have also been done using "natural experiments" and time series data, which had findings similar to the cross-sectional studies. However, George Borjas, of Harvard University, and several other economists have used time series studies and looked at wage inequality data and found that immigration does have a significant effect on domestic laborers. There are several factors, however, that might lead to the overestimation of the effects of immigration using the wage inequality methodology. The primary problem in past studies was the limitations on available data. The wage inequality studies may therefore represent an upper boundary for what the real effect of immigration is on domestic wages. International borrowing and lending International borrowing and lending is another type of international factor movement; however, the "factor" being moved here is not physical, as it is with labor mobility. Instead, it is a financial transaction. It is also known as portfolio investment. International lending takes place through both private, commercial banks and through international, public banks, like multilateral development banks. It can be classified as a type of intertemporal trade, i.e., the exchange of resources over time. Intertemporal trade represents a tradeoff of goods today for goods tomorrow, and it can be contrasted with intratemporal trade, an exchange of goods taking place immediately. Intertemporal trade is measured by the current account of the balance of payments. According to the time value of money, the present value of money is not equal to its future value (e.g., $1000 today is worth more than $1000 a year from now). Those wishing to borrow money from a lender must provide a measure of compensation above the value of the principal being borrowed. This compensation usually happens in the form of an interest rate payment. People do not all have the same demand for present and future consumption, so if borrowing and lending are allowed the "price of future consumption", i.e., the interest rate, will emerge. For the purposes of international economics, countries can be thought of in the same way as people. If a country has a relatively high interest rate, that would mean it