Despite the bump after last week's US midterm elections, this week the S&P 500 (.INX) has fallen over 3% from 2,800 to the 2,700 level. While President Trump has blamed the slump on the Democratic Party's threats to investigate his tax returns and other potential scandals, market analysts blame a strong dollar, oil bear market, and the tech sector.

The US dollar (USD) rose to its highest level in 16 months as investors fear uncertainty surrounding the UK's Brexit deal with the EU. The Federal Reserve has not helped, sticking to its schedule of gradual rate hikes even as Trump repeatedly criticizes Chair Jerome Powell for his hawkish monetary policy. The market expects another rate hike in December. While a stronger dollar is good for tourists and companies that import, it hurts American companies that export and sell in foreign countries. Firms in the S&P 500 earn 44 percent of their sales outside the US, especially in the tech, energy, and industrials sectors. A strong dollar makes American goods and services more expensive to buy overseas, so less demand means worse sales and market share.

Surprisingly, oil has also entered a bear market. West Texas Intermediate crude oil fell for twelve straight trading sessions to $55.69 a barrel. Five factors are behind the oil bear market. First, there is oversupply in the market from OPEC's increased September production by 100,000 barrels per day. Second, Trump gave waivers to eight countries to allow them to continue buying Iranian oil despite fresh sanctions. Third, Trump has repeatedly called for cheaper oil this year in tweets. Fourth, US oil production hit a record 11.6 million barrels per day in November, saturating an already oversupplied market. Fifth, crude inventories from refineries have grown more than expected for the winter season. All that means crude oil has begun trending downward, and dragging energy stocks and the stock market with it.

Finally, tech is struggling amid concerns about global growth. It has underperformed the S&P in the last few weeks, thanks to woes from the largest firms. Apple (AAPL  ) is no longer a trillion-dollar company after its rout to under $190. On Monday, Apple supplier Lumentum disclosed that its largest customer reduced orders, prompting speculation and a 5% drop in Apple shares. Guggenheim downgraded Apple stock to neutral, and UBS (UBS  ) and Goldman Sachs (GS  ) lowered their price targets and iPhone sales estimates. Amazon (AMZN  ), Micron (MU  ), AMD (AMD  ), and the broader stock market fell in unison with Apple. Growth concerns in developing economies like China are one of equities investors' biggest fears.

The 2,700 and 2,600 levels are key supports for the S&P 500 and will likely reveal whether the dip is overblown or a step into a longer bear market.

The author owns a small long position in AAPL and MU.