U.S stocks have been on the decline during the week of Jan. 25 to Jan. 29 as a result of increased market volatility. This is due to speculative trading by retail investors.

On Jan. 29, the Dow Jones Industrial Average dropped 2%, the S&P 500 fell 1.9%,below its 50-day moving average, and the NASDAQ Composite fell 2%. These declines can be attributed mainly to the large magnitude of retail investors trading in heavily shorted stocks such as Gamestop and AMC Entertainment.

These retail investors are executing a “short-squeeze,” where they buy large quantities of a heavily shorted stock, causing the stock to increase in price and eventually forcing short sellers to buy stock to hedge their initial short. This will result in the price increasing even more.

This short squeeze has negatively affected numerous hedge funds such as Citron Research and Point72, which held large short positions on the stock. Gamestop short-sellers are losing over $19 billion this year according to data from Ortex.

The hedge fund that bore the brunt of the damage and fed into this short squeeze the most, however, is Melvin Capital. Melvin Capital lost 53% of its investments in the month of January, according to The Wall Street Journal.

The hedge fund seemed to have learned its lesson, however, as they closed all of their short positions in Gamestop on Jan.27 and greatly lessened the risk in their portfolio, which previously made most of its gains through shorting.

The rise of Gamestop has increased worries that there is a potential bubble in the market as stock prices become more and more expensive compared to their valuations, with levels coming close to those preceding the dot-com bubble crash in 2001. Despite this, the Chairman of the Federal Reserve Jerome Powell has insisted that the stock market is in a healthy position and “vulnerabilities are overall moderate.”

Looking past the retail-fueled frenzy on Gamestop, AMC and others, earnings season continues, with reports coming out from Apple Inc., Microsoft Corp., Tesla Inc. and Facebook Inc. indicating a drop in each of their respective stocks..

Apple, although posting higher than expected sales due to its strong sales growth of iPhones in China, saw their stock fall as a sell-off occurred. This, combined with comments from CEO Mark Zuckerburg criticizing Apple and a potential Facebook lawsuit, caused the stock to drop even lower, down 10% since the start of the week.

Apple started the week off at $143.00 and ended at $131.96, with a week high of $144.96.

Facebook has also seen its stock drop after decent earnings. This is mainly due to Apple and the changes to its ad-tracking technology that it plans to implement. This change would negatively affect Facebook’s ad targeting, hurting the main revenue source of the company.

Facebook started the week off at $278.35 and ended at $258.33, with a week high of $284.56 Microsoft also posted higher than expected sales in its earnings report, resulting in its stock increasing throughout the week before slightly dropping on Friday due to a sell-off fueled by fears regarding market volatility, according to CNBC.

Microsoft started the week off at $228.82 and ended at $231.9, with a week high of $242.46.

Tesla fell short on its earnings, despite a growth in revenue that beat estimates and another profitable quarter. Their stock also fell throughout the week, mainly suffering from what is plaguing the other companies mentioned, a sell-off fueled by fear of volatility. Tesla started the week off at $854.42 and ended at $793.53, with a week high of $895.70.

The main focus in the coming week is the actions of retail investors fueling market volatility. In addition, more earnings calls from companies such as Amazon.com Inc., Alphabet Inc., Pfizer Inc. and PayPal Holdings Inc. will be released on Feb. 2.