Just because a chart is correct, it does not mean it's not misleading. Here's an example: Back in the USA, on March 12, US Senator Ted Cruz and NASA Administrator Charlie Bolden went head to head at a hearing on the President’s FY2016 budget request arguing as to what they thought NASA’s priorities are today. Sen. Cruz is known to be a climate-change skeptic and has often said that NASA should focus on space exploration and leave earth science to other agencies. Although Cruz and Bolden disagreed strongly, reports are that the hour-long meeting was nonetheless cordial. The interesting part of the hearing for me was the ridiculous bit of chartsmanship that Sen. Cruz employed to kick off the meeting. A few minutes into the hearing, Sen. Cruz had an aide lumber over to the poster stand to display the large printed poster board pictured below.


Chart displayed at the hearing on the President’s FY2016 budget request on March 12, 2015. Typically, bars are arranged in ascending or descending order, but here it seems they were trying to contrast Earth Science vs. Exploration & Space Operations. Note the Earth clip art added to emphasize the answer to their own question.

As Sen. Cruz looks at the chart he says, "In my judgement [this chart] does not represent a fair or appropriate allocation of resources. That it is shifting resources away from the core function of NASA to other functions." Later the senator says, "the chart does not suggest that the investment of budgetary resources is going where it should." The implication is that money previously used for space exploration has been reallocated to earth science. It seems that senator Cruz feels this chart is the smoking gun to support his idea that NASA has lost its way by focusing on earth science rather than remaining focused on space exploration. (Watch a 9-min clip from the beginning of the hearing.)

You can fool some of the people...
A lot of people may find this kind of data display convincing today. In fact, you could imagine a newspaper headline which read "NASA Shifts Priorities from Space Exploration to Earth Science" accompanied by this kind of chart. At first glance, the visual of a dramatic increase in earth science allocations while showing a decrease for space exploration may feel like it supports the Senator's claim. This kind of chart may work in a TV infomercial or a cable news talk show where viewers do not pay close attention and are easily fooled by fast-pitched unfounded claims and spurious relationships, but in a setting like this, the chart was utterly unconvincing, especially to the retired United States Marine Corps Major General, and former NASA astronaut Administrator Bolden. (Update, apparently you can fool some of the people.)

The figures in the chart are correct, but they're terribly misleading. The two major problems with the chart are that (1) showing only percentage increases over the last seven years says nothing about the actual dollar amount being allocated to each category nor its relative percentage to the entire NASA budget. (2) Even if we were to agree that percentage increases or decreases of allocations necessarily translated into relative importance or priorities, we do not know what was even included for the the category of Space Exploration. Depending on what you include, you could actually show that there was a percentage increase for space exploration. More importantly, since 2009, the Space Shuttle program retired. The Space Shuttle was obviously expensive so if you remove it—sometime after 2011—then that would surely impact the budget for exploration. Also, allocations for earth science research were cut significantly during the previous US administration, so an increase since 2009 would not be surprising. Yet, as a percentage of the entire NASA budget, the earth science allocation in 2016 is actually less than in the year 2000. This also does not support the idea of a “disproportionate increase” in earth science.

Additionally, Bolden stated that NASA was intentionally aiming to reduce the cost of space exploration. But a slight reduction—even if it were true—would not mean space exploration was any less of a priority or that funds were being diverted from exploration to earth science, something Sen Cruz was implying that the chart showed. After vigorously defending the earth science programs, Administrator Bolden said this:

"You asked me about your chart. There's a lot of chartsmanship [in that chart]. I'm not sure what you include in Exploration, so by my statements I was not acknowledging that I agree with the numbers in the chart. I don't want anyone to say that I accept the numbers on the chart."

Another way to look at it
Although Sen. Cruz's chart was not incorrect, it was still be terribly misleading. So using the same categories that Sen. Cruz used in his chart, which does not include all of the budget request categories, I made two versions of a similar bar chart. But by focusing on the actual numbers requested, this slide suggests a different story and supports the idea that NASA's budget is focused on exploration and space operations.


Instead of a poster board on an easel, why not equip the hearing room with large digital displays where data can be accessed and easily displayed. In this case, the NASA Administrator could have shown his own charts to show a clearer picture.


This shows that Exploration & Space Operations is by far the biggest category. Two colors for the bars were chosen directly from the photo of Jupiter which was taken by NASA's Cassini spacecraft. The photo and Cassini being examples of exploration or "focused outward."


In this example of the same chart the bars are arrange horizontally. The colors were taken directly from the NASA logo. The emphasis is on Exploration & Space Operations, and the red color—and the much greater length—make the top bar pop.


Does not get much simpler than this. Even though funding for Earth Science is crucial, this chart suggests it hardly holds a "disproportionate" slice of the NASA budget pie. An even better graph would be of a line chart that showed the 10.5% of 2016 is actually down from around 12.4% in 2000.

• Five simple rules for making awesome bar charts.