Even with Apple, the Dow would still be meh

For all of the excitement about Apple joining the Dow Jones industrial average next week, it might not make such a big difference.

In fact, had the Cupertino, California tech behemoth been in the group since the start of the year, the index still would be struggling to get into positive numbers, according to computations by brokerage firm Convergex.

As of Wednesday's close, Apple's $143 share price, including a 12 percent year-to-date gain, would have added just 82 points to the price-weighted index—a nice gain but barely enough to pull the average to level ground in an up-and-down year for the market. The Dow was off 187 points for the year heading into Thursday trading, which saw a nice rally on Wall Street that brought the industrials to around even in 2015.

"To get the Dow moving higher, you'll need some of the heavyweights in this price-weighted measure to get moving," Nick Colas, the chief market strategist at ConvergEx, said in his morning note Thursday.

Nasdaq congratulates Apple for joining the Dow Jones industrial average.
Nasdaq congratulates Apple for joining the Dow Jones industrial average.

The Dow, which gets most of the market headlines, differs from the S&P 500, which is a much broader assessment of market conditions, in one key way: It is price weighted, rather than cap-weighted. The difference is that companies with higher share prices will have a bigger impact on the Dow, while those with higher total worth i.e. market capitalization exert greater force over the S&P 500.

So even though Apple is the largest company in the world with a $712 billion market cap, it only has a 4.3 percent weighting in the Dow.

Still, Apple's 82-point boost to the Dow would place it second for the year among the biggest contributors, behind only Boeing, which had added 144 points as of early Thursday trading, according to FactSet. The next biggest contributor was United Health, with 81 points, followed by Walt Disney, with 68 points.

The biggest drag on the Dow has been American Express, with a subtraction of 74 points, with Caterpillar next at 72 points. Dow additions are calculated using share price times a divisor, which currently is 0.155716585.