When it comes to the Bureau of Labor Statistics’ “First Friday” unemployment numbers, March’s data are a good reminder of our monthly mantra: don’t read too much into any one set of numbers, based on two very different surveys, both themselves based on samples of much larger populations.

That said, no matter how humbly provisional I know I should be, I have a less exuberant reaction to the March numbers than some commentators seem to. They point to the healthy number of jobs created — 192,000 — and the upward revisions of the past two months’ numbers — 37,000 more jobs added than originally reported during the winter.

And there were other bright spots, notes Wellesley’s economics department chair Kristin Butcher, whom I interview on the NewsHour Friday: temporary jobs were up in March, and they tend to be a “bellwether” of future job growth, as do construction jobs, which are also up.

But overall, Butcher views March’s numbers as I do: with caution. That’s because, according to the survey of 60,000 households, roughly 170,000 more Americans of working age were added to the population in March, consistent with the number we add just about every month, and also consistent with the Census Bureau’s report that the U.S. population is growing at slightly more than 2 million people a year.

But that would mean that the number of jobs added — 192,000 — just kept pace with the number of new people who needed them. And sure enough, that would explain why the total number of people who told interviewers that they hadn’t worked even one hour in the previous week — the total number of officially “unemployed” in America — barely budged, and is still well above 10 million.

As Making Sen$e regulars know, we also keep track of a more inclusive measure of unemployment which we call U-7: the total number of Americans who say they want a full-time job but don’t have one. That number rose in March, for the first time since October, to nearly 24 million. That is a lot of people.

So what happened to explain the rise? Well, a lot of it seems to be because the number of part-timers who want a full-time job swelled. The BLS news release claims that “The number of persons employed part time for economic reasons (sometimes referred to as involuntary part-time workers) was little changed at 7.4 million in March.”

But in fact, if the BLS’ Table A-8 is to be trusted, the number of part-timers wanting full-time work number rose from 7.168 million Americans to 7.411 million in just the one month of March. That’s an increase of more than 3 percent. Yes, it could be a statistical “artifact” as they say: a more or less random number. But it also could be a sign of employers running from the Affordable Care Act, or a wobbly underbelly to an otherwise optimistic body of data.

Paul Solman spoke with “Leading Indicators” author Zachary Karabell last month about our obsession with economic statistics like the unemployment rate.

