Although consumers remain confident, last week’s data showed that neither consumers nor businesses are spending. This weakness raises concerns about whether the expansion will continue to accelerate.

It’s hard to believe tomorrow is July 1—the halfway point of 2017. The first half of the year, eventful as it was, has simply blown by. And now that we are moving into the second half, it’s time to take a look at the stories that are likely to play out in the economy and markets over the next six months.

Yesterday, we talked about the worries surrounding exchange-traded funds (ETFs)—chiefly, that they could trigger a flash crash. Ultimately, we concluded that ETFs are just an enabling technology, not the real problem. The real problem, at least potentially, is passive investing. Let’s take a closer look at what the passive investing trend could mean for the markets.

It’s never the bus you’re watching for that hits you, they say. Even if you are watching for different buses, sometimes it pays to look at just how close they are getting to you. In that spirit, and in response to some questions I have gotten recently, let’s look at two different buses that could run over the markets: exchange-traded funds (ETFs) and passive investing.

Recently, there has been a great deal of discussion over oil prices—up, down, in a bear market, what is OPEC doing? So, let’s see what we can discern by applying our usual methods to the situation: evaluating changes over time, rather than in the short term; applying some historical perspective; and then looking at the fundamental economic realities to figure out what they mean now and in the future. I think you will find the results interesting.

Last week was a slow one, primarily focused on housing, with reports on sales of existing homes on Wednesday and new homes on Friday. Unlike much of the news recently, the data showed that housing continues to do well, with strong demand and activity.

In yesterday’s post, I explained that the noise in returns—in other words, how much they bounce around—is what imposes much of the risk when investing over shorter periods. When you might lose 20 percent or more in a year, any plans that start soon thereafter can be derailed. Volatility (i.e., the noise) is a real drag in that sense.

One of the key points I made in yesterday’s post was about your time horizon, and how shorter time frames call for more caution than do longer ones. But this is actually a bigger point, which applies to multiple areas of investing and life. So, I thought I would make the discussion more general.

From our recent analysis, we can conclude that stock market risk is high. We can conclude that, even if things are different this time, they probably aren’t different enough to make a meaningful change in the outcome. And we can conclude that 2017 might well be 1999 all over again.

In several recent posts, I have made the case that today’s economy looks quite a bit like 1999—and that the markets may be setting up to look like 2000. Although this argument certainly seems reasonable, we have to ask ourselves how it could be wrong. Despite all the similarities, could it be different this time? If so, how? And what would that mean?