Japan in the 1980s experienced a "bubble" economy, as the stock market index soared from 6000 in 1980 to 40,000 in 1989. Simultaneously, Tokyo experienced a huge increase of urban land prices. This "land bubble" phenomenon led to new strategies in the urban development process. In order to preserve the profitability of real estate schemes, developers used several means of action to increase building density, namely the jiage system and urban renewal procedure. They also experimented with new methods to avoid land purchase, such as land deposit and short-term lease contracts. These new methods of development had a great impact on Tokyo's morphology. Skyscrapers and high-rise buildings were built in business zones instead of narrow "pencil buildings"; huge department stores surrounded by public squares flourished in the vicinity of middle-range railway stations; and modern concrete buildings progressively replaced old wooden houses within residential zones. However, this modernization process was not closely controlled by the public authorities, and it produced an anarchic collection of high-rise buildings throughout the capital city that increased road traffic and worsened parking problems.