Volkswagen's stock performance experienced a significant decline immediately after the emissions scandal news broke in September 2015. The scandal, which involved the company admitting to using software to cheat on emissions tests for diesel vehicles, led to a sharp drop in investor confidence.

On September 18, 2015, the day the scandal was revealed, Volkswagen's shares fell by about 20% in just a few days, wiping out billions in market value. By the end of September 2015, the stock had lost nearly a third of its value compared to its pre-scandal levels. The fallout continued for months, with the stock price remaining volatile as the company faced legal challenges, regulatory scrutiny, and a tarnished reputation.

This incident not only affected Volkswagen's stock but also had broader implications for the automotive industry, particularly regarding diesel technology and regulatory practices. The scandal ultimately led to significant financial penalties and a shift in the company's strategy towards electric vehicles.

For more detailed information, you can refer to financial news archives from that period, such as articles from Bloomberg or Reuters, which covered the immediate impact on Volkswagen's stock and the subsequent developments.