The U.S. stock market made an alarming fall for the second day in a row, creating more worries that China's slowing economy would take America down with it.

The Dow Jones Industrial Average — a basket of 30 of America's most iconic companies — fell 529 points in value during the day, with the Nasdaq, which is more representative of tech stocks, fell 171 points. Both dropped more than 3%.

Those are enormous losses for a stock index, more indicative of a panic or crisis rather than a bad day in the markets. The drop caps one of the worst weeks for the country's main indices since the financial crisis.

The S&P 500, the most closely watched U.S. stock index, fell 3.2%, adding to what had already been a brutal week.

Some companies were hurt more than others.

Media and technology stocks, which often fair particularly poorly in down markets, have been getting hammered. Netflix, which had been enjoying an especially strong 2015, has born the brunt of the sell off. Its shares have now dropped more than 15% since their mid-August peak.

Tech stocks were broadly lower, with Apple, Amazon Google, Microsoft, and Facebook all down by at least 3%.

The recent decline in U.S. stocks has been closely tied to global problems, most notably in China, which is experiencing an all-out market crash.

The Shanghai Composite Index (the country's most closely watched group of stocks) suffered another brutal day, dropping 4.3% on Friday. The index has lost almost a third of its value since mid-June.

In addition to China, continued declines in the price of oil have also led to some concern about a global economic slowdown. Oil fell below $40 per barrel for the first time since 2009.

The market turndown is not just bad for major U.S. companies. As venture capital investor Bill Gurley warned on Twitter, stock downturns can have an impact on startups looking to raise money.

4/ One might reasonably assume that this would have an adverse impact on late stage private market liquidity and valuation. I certainly do. — Bill Gurley (@bgurley) August 21, 2015

Not everyone was ready to panic. Some pointed to positive economic data including solid job reports as evidence that the U.S. was fundamentally sound.