Citing data is an effective debating technique in the right context. Many well-educated people take pride in being "data-driven" and consequently give a lot of weight to arguments that involve numbers.
That deference leads smart people to ignore things that would otherwise be obvious. I don't mean that they skip the p-value calculations or ignore sampling bias or anything like that. Instead, they forget about the basics of counting.
The example that follows is political; my point isn't.
Around the time Trump was inaugurated, I saw many friends sharing an article entitled "Obama issued fewer executive orders on average than any president since Cleveland." They shared the link to respond to the common claim that President Obama exercised his executive power too aggressively. The article is well written, it comes from a respected, non-partisan source, and it sticks to well-researched facts.
It's also basically wrong. The numbers are correct as far as they go, but the article demonstrates two classic rules:
1. Don't count apples and oranges. Here's why the article is misleading: In February 2014, Obama signed two Executive Orders two days apart.
One of the two increased the minimum wage for federal contractors. That order directly affected hundreds of thousands of workers. The symbolic impact may have been even bigger, as headlines around the country described it as a big step in the push for a higher national minimum wage.
The other order changed the name of the name of the "National Security Staff" to the "National Security Council Staff." Although that order didn't draw headlines, it's believed to have affected as many as a dozen business cards.
The impact of Executive Orders varies widely, with some being trivial and others changing the course of history. Counting the number of Executive Orders issued by a president is a silly exercise. But that's precisely what the article linked above does. The results are predictably silly. For instance, their chart shows that over the last 150 years, no president who served a full term issued fewer executive orders than Lincoln. Never mind that Lincoln issued two of the most important executive orders of all time with the Emancipation Proclamation of the suspension of habeas corpus.
2. Don't count the wrong things. Even if all Executive Orders were created equal, the article would still be misleading. Here's a pop quiz: What was Obama's most important Executive Order? If you said creating the DACA program, you're... dead wrong. Despite many headlines suggesting otherwise, DACA was implemented via an Executive Memorandum, not an Executive Order. Consequently, it wasn't included in the figures used by that article. Presidents have many ways to exercise their power, so counting Executive Orders even less useful than the last section implied.
The point isn't about Trump or Obama or even Executive Orders. The point is that you can't track your spending by counting how frequently you use your American Express. Framing it as "using data" doesn't change that.