# Today’s Morning Waker-Upper: The Great Dual Y-Axis Dispute

Today let’s discuss one of the great blogging controversies of our time. Having dispensed earlier with the Oxford comma (yes) and how to treat the word data (it’s singular), it’s time to take on the great Dual Y-Axis Dispute.

I’ll illustrate this with a chart I made up. Suppose I want to show that economic growth leads to high employment. Does this do the job?

This chart does indeed show both GDP growth and employment, but it’s almost impossible to tell if they’re related in any way. To show them both, the chart has to scale all the way to 100 percent, but when the scale is that large you can barely even see the peaks and valleys, let alone whether they’re related. So instead I can do this:

By using one y-axis for GDP growth (on the left) and another for the employment rate (on the right), you get a good view of how and when each of them has gone up and down. It’s now clear there’s a relationship, as you’d expect, but it’s also not perfect. Why did the huge Reagan expansion produce only modest employment growth? Conversely, why has the modest Obama/Trump expansion produced huge employment growth? Seeing the data presented this way helps to make things clearer and can spur further questions.

Now, there’s no question that a dual y-axis can be confusing. It’s just not something we’re used to seeing. I always try to make my dual-y charts easier to read by labeling them in different colors so it’s immediately obvious which line goes with which data series. I also do my best to adjust the axes so that the numbers on both sides line up properly with the gridlines.¹

So the question is: Does the clearer presentation of the relationship make up for the added complexity of the chart? And is there a better way to show it? I’d answer definitely yes to the first question, and usually no to the second. Sometimes there is a better way, but not always. Sometimes it’s either a dual y-axis or nothing.

And, really, what’s the objection? I’ve been a big fan of chart guru Edward Tufte for decades, and his mantra was to simplify as much as possible and to ruthlessly eliminate “chart junk.” This is good advice, but ever since Tufte became popular it’s become advice that many people take too far (as Tufte himself did later in life, I think). Eventually you get to the point where you’re making it harder to read a chart because it’s become so spare that it lacks the visual cues readers expect. You can eliminate gridlines entirely, for example, but that makes it harder on the reader who wants to look at a chart carefully and get a real sense of the data behind it. When you sacrifice that, you can easily end up with a wiggly curve that’s more just a directional symbol (something is going up, or down, or U-shaped) than a true chart.

So that’s my take on dual y-axis charts. Yes, they add some clutter and complexity. Yes, they can be confusing to a casual reader. You should do your best to address that. But sometimes it really is the simplest, least cluttered way of making a point. When that’s the case, don’t let either personal dislike or the misplaced authority of Edward Tufte stand in the way of using them.

¹FWIW, this is harder than it sounds.

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### WE'LL BE BLUNT

It is astonishingly hard keeping a newsroom afloat these days, and we need to raise \$253,000 in online donations quickly, by October 7.

The short of it: Last year, we had to cut \$1 million from our budget so we could have any chance of breaking even by the time our fiscal year ended in June. And despite a huge rally from so many of you leading up to the deadline, we still came up a bit short on the whole. We can’t let that happen again. We have no wiggle room to begin with, and now we have a hole to dig out of.

Readers also told us to just give it to you straight when we need to ask for your support, and seeing how matter-of-factly explaining our inner workings, our challenges and finances, can bring more of you in has been a real silver lining. So our online membership lead, Brian, lays it all out for you in his personal, insider account (that literally puts his skin in the game!) of how urgent things are right now.

The upshot: Being able to rally \$253,000 in donations over these next few weeks is vitally important simply because it is the number that keeps us right on track, helping make sure we don't end up with a bigger gap than can be filled again, helping us avoid any significant (and knowable) cash-flow crunches for now. We used to be more nonchalant about coming up short this time of year, thinking we can make it by the time June rolls around. Not anymore.

Because the in-depth journalism on underreported beats and unique perspectives on the daily news you turn to Mother Jones for is only possible because readers fund us. Corporations and powerful people with deep pockets will never sustain the type of journalism we exist to do. The only investors who won’t let independent, investigative journalism down are the people who actually care about its future—you.

And we need readers to show up for us big time—again.

Getting just 10 percent of the people who care enough about our work to be reading this blurb to part with a few bucks would be utterly transformative for us, and that's very much what we need to keep charging hard in this financially uncertain, high-stakes year.

If you can right now, please support the journalism you get from Mother Jones with a donation at whatever amount works for you. And please do it now, before you move on to whatever you're about to do next and think maybe you'll get to it later, because every gift matters and we really need to see a strong response if we're going to raise the \$253,000 we need in less than three weeks.