While uncertainty has thrown the market into volatility this year after its relatively smooth sailing nine-year bull run, various ups and downs have for the most part leveled off returns in 2018. As for the Dow Jones Industrial Average (DJIA), up about 1.2% year-to-date (YTD), compared to the S&P 500's 3.6% increase over the same period, solid performance from just two stocks are responsible for carrying the index, according to FactSet data and as reported by CNBC. (See also: The Bull Market Turns Nine: A Look at the Top Performers.)

Out of the 30 companies in the blue-chip index, Goldman Sachs Group Inc. (GS) and Boeing Co. (BA) have been responsible for nearly all of the index’s gains in 2018. Other powerhouses in the DJIA, such as smartphone maker Apple Inc. (AAPL), JPMorgan Chase & Co. (JPM) and Visa Inc. (V), have traded about flat throughout the first two months and a half of the year, in terms of point contribution, based on the FactSet data.

As of the start of this week, jet maker Boeing had contributed 316.5 points to the Dow, while Goldman contributed 119.5. McDonald's Corp. (MCD), one of the biggest drags on the index, took away 92 points, while consumer goods giant Procter & Gamble Co. (PG) subtracted 76.

Blue-Chip Blues

All of the other companies lie somewhere in the middle regarding their impact on the Dow. While some have posted strong gains in 2018, such as legacy tech titans Cisco Systems Inc. (CSCO), up about 20% YTD and Microsoft Corp. (MSFT), which has grown over 11% over the period, the relative cost of their shares make their impact smaller than their DJIA peers. 

Boeing, trading down about 1.5% on Wednesday morning at $333.71, reflects an approximate 13.2% gain YTD. Wall Street's Goldman Sachs has returned 5.8% in 2018, trading up 0.4% at $269.50. Both companies are market leaders in their respective industries and have been highlighted by analysts as two of the major beneficiaries of the recently passed GOP tax overhaul, set to slash the corporate tax rate near 20% and incentivize billions in overseas cash repatriation. (See also: Trump ‘Very Serious’ About 'Phase 2' of Tax Cuts.)