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Dow 20K: Are we there yet?

The Dow Jones industrial average has been closing in on 20,000 for over a week now and was as close as 27 points Tuesday morning. Market observers and investors alike have been hotly anticipating that new threshold, but the index just hasn't been able to make it over that hump.

Surprisingly, it was less than $10 in real share price that separated the Dow from breaking that barrier, as of the close Friday.

If any one of the 30 Dow stocks increased in value by $9.67, the index as a whole would rise above 20,000. Put another way, if each stock increased by just 33.3 cents, it would break the barrier. That's because a single-dollar movement in any one stock is worth 6.8 points to the index because of how it's created.

Note: Prices in this table may be delayed.

The Dow is different from other indexes like the S&P 500 in that it's a price-weighted index, meaning that the higher a stock's share price, the more important is is to the index as a whole. Essentially, the Dow is calculated like a portfolio of one stock from each of the 30 companies.

In order to absorb the changes when companies are added or a stock is split, that sum of the 30 share prices is divided by the Dow divisor, which is currently 0.14602. That means a $1 move in a single stock is worth around 6.8 points to the index itself.

Of course, a $1 change in the price of a cheaper stock like GE is proportionately bigger than that same move in a behemoth like Apple. That's one reason a lot of indexes — like the S&P 500 — adjust their values based on a company's market cap so big companies wield greater influence, regardless of their per-share price.

Obviously, not every stock is worth the same. That $9.67 added to Traveler's per-share price is only worth $2.7 billion in market cap. That same move for Goldman Sachs or Caterpillar would be worth under $6 billion. Those stocks have high share prices but relatively low market caps. So it could be a much smaller trade pushing those share prices higher and helping the whole index over 20,000.

On the other hand, there are some companies with low share prices and high market caps. That same shift in share price is worth a ton, and a lot harder to find. Look at Microsoft and Pfizer: That nearly $10 move is worth $75 billion to the software giant and $58 billion to the pharmaceutical company.

For GE, that $9.67 move would be worth $86 billion in market cap.