Pisani: Here's what will move stocks in 2017
Pisani: Here's what will move stocks in 2017 · CNBC

I noted yesterday that the market debate was between "pragmatists" and "optimists" over two 2017 issues:

1) Will consumer confidence remain high and, specifically, will the Trump rally translate into more consumer spending?

2) How much will expectations for tax cuts and fiscal stimulus impact earnings in 2017 and 2018?

Here's my concern: Investors seem wildly optimistic. Consumer sentiment and business sentiment surveys have all popped after the election. The recent National Federation of Independent Business survey, for example, found dramatically different attitudes among small business owners before and after the election.

Investors are not just expecting a rally — we've already had that — they are expecting some kind of global reflation to occur.

I'm wondering where it will come from. Let's look at the evidence presented so far.

1) Consumer spending will increase. Will it? We could get a cut in the personal income tax, or consumers may simply feel better and begin spending more of their savings.

Let's put aside the personal income tax cut, since we have almost nothing to go on. PIMCO's Tony Creszenzi visited the New York Stock Exchange recently. I asked him for a back-of-the-envelope calculation of how simply spending more and saving less might help the economy.

He noted there was roughly $15 trillion in personal income each year. A roughly 6 percent savings rate produces savings of $900 billion a year. Consumers can spend more by drawing on the existing stock of savings or can boost spending by simply reducing how much they save.

So let's assume consumers spend 1 percent more by reducing their savings rate from 6 percent to, say, 5 percent. That's an additional $150 billion of spending. Annual consumer spending is roughly $5.2 trillion, so we're talking about a boost of about 3 percent.

That may not seem like a lot, but a 3 percent boost is significant.

Impact on earnings: moderate. This could definitely produce an increase in earnings, but as we saw this year the benefits are likely to accrue to a small group of retailers and potentially automotive stocks as well as restaurants and travel stocks.

2) Corporate tax cuts: Of all the "hopium" the market has been trading on, this is the one that has the best chance to move the dial on earnings.

Even before the election, analysts were anticipating a roughly 9 percent increase in earnings for the S&P 500, from roughly $118 in 2016 to $131 in 2017. But I noted back on Dec. 1 that Thomson Reuters estimated that every 1 percentage point reduction in the corporate tax rate could "hypothetically" add $1.31 to 2017 earnings. So with a full 20 percentage point reduction in the tax rate (from 35 percent to 15 percent), that's $1.31 x 20 = $26.20.