A man walks by the New York Stock Exchange in New York City.

The earnings picture is getting complicated.

As earnings season kicks off Friday, investors are debating the impact of an unusually large number of variables, including higher rates, higher raw material costs, weaker foreign currencies, tariffs and weaker demand from China.

One thing's for sure, investor attention is focusing away from third- and fourth-quarter earnings (both of which will be outstanding) and toward 2019 projections.

Let's look at the major issues.

1. Margin erosion. This is principally about higher costs in wages and raw materials. Amazon's announcement of a $15 minimum wage will not affect third- or fourth-quarter earnings, but it has everyone scrambling to figure out what the impact might be in 2019.

The good news on higher costs is that many companies are trying to pass them on to customers with price increases.

There's one other saving grace to keep margins up, and that's higher revenue. The S&P is seeing revenue growth this year close to 9 percent, well above the average of the last few years, and will likely see growth of about 7 percent in 2019.