Margin lending became popular in the late 1800s as a means to finance railroads. In the 1920s, margin requirements were loose. In other words, brokers required investors to put in very little of their own money, whereas today, the Federal Reserve's margin requirement (under Regulation T) limits debt to 50 percent. During the 1920s leverage rates of up to 90 percent debt were not uncommon. When the stock market started to contract, many individuals received margin calls. They had to deliver more money to their brokers or their shares would be sold. Since many individuals did not have the equity to cover their margin positions, their shares were sold, causing further market declines and further margin calls. This was one of the major contributing factors which led to the Stock Market Crash of 1929, which in turn contributed to the Great Depression. However, as reported in Peter Rappoport and Eugene N. White's 1994 paper published in "The American Economic Review", "Was the Crash of 1929 Expected", all sources indicate that beginning in either late 1928 or early 1929, "margin requirements began to rise to historic new levels. The typical peak rates on brokers' loans were 40–50 percent. Brokerage houses followed suit and demanded higher margin from investors".