In many ways, stock market commentators have an unenviable task.  At any given moment they have to come up with new and interesting reasons why stocks are rising or falling.   The media gurus’ difficulties are compounded by the fact that most are story presenters who have little understanding of investing and are therefore reliant on sources whose statements are many times influenced by their own private agendas.

After peaking in mid-September, US stocks have fallen by about 7% through yesterday/  This has erased most of their year-to-date price gains, although with dividends factored in the S&P is still up about 4% since New Year’s Day.

Among the current “explanations’ for the fall are:

–a falling oil price.  I don’t think this makes sense.  It would be one thing if world GDP were turning negative and demand were sagging as a result.  The current issue, however, is oversupply, being caused by the rise of shale oil/gas production in the US.

Yes, 10% of the S&P 500 consists of oil-related stocks, many of which are hurt by lower prices.  But, to simplify a bit, the other 90% of the index is a beneficiary.  Lower prices are bad for oil-producing nations in the Middle East, for Russia and for the rest of OPEC.  But they’re great for consumers.

Another point:  today’s production contracts with national oil companies provide that virtually all revenue from oil price increases above a certain level goes to the host country, not to the international oil firm that is developing the petroleum deposits.  Although this has been true for decades, my sense is that many investors still don’t get this.  The dynamic is much more consumers gain/emerging countries lose than the consensus thinks.

–ebola.  More about this tomorrow.  Ebola is scary.  The only model we have for what happens to stocks once investors become aware of pandemic possibilities is SARS.  On the other hand, Doctors Without Borders has been handling ebola patients for many years without a single infection of their own.  In my view, stocks would be way lower than they are today if investors viewed ebola a real threat.

–the dollar.  This is an issue, although almost no one is talking about it. The US dollar has risen against the euro by almost 10% since early May.  In back-of-the-envelope terms, 25% of the earnings of the S&P 500 is sourced in euro.  A 10% fall in the dollar value of the euro means that overall S&P earnings–without factoring in current Euroland economic weakness–will be 2.5% lower than previously thought.  Discounting this outcome would explain about half the recent market decline.

my take:

–technicals.  At the peak a few weeks ago, stocks had already discounted all the S&P earnings growth that’s likely for 2014.  In addition, the market had already also factored into prices, let’s say, a third of the expected earnings growth for the index next year. This is normal market behavior, granted, though, that we haven’t seen “normal” for the better part of a decade.

By September, potential short-term buyers couldn’t justify paying higher prices for stocks.  In addition, euro weakness + a lot of other miscellaneous stuff had put 2015 profits under threat.

We’re now in the process of determining how low prices have to go to bring buyers back.

Looking at past levels where lots of buying and selling has taken place ends up being a surprisingly effective tool for figuring out where buying will emerge again.  Don’t ask me why.  If this rule of thumb holds true, as I read the charts the key levels are 1840-80 (i.e., where we are as I’m writing this) and 1800.