Actually, DK, it's more a sign of vast changes in the publishing industry. The truth about magazine size is that it's NOT driven by the amount of activity going on in the market that it serves -- i.e. manufacturing activity.
It's driven by the amount of advertising purchased by the people who want to reach the readers of the magazines.
A few things have happened in the days since American Machinist and Welding, as 2 examples, were routinely much fatter than they are today.
1) Reduced barriers to entry: Once upon a time, American Machinist was the only publication serving its market. More recently, it was one of a small handful. Today it is one of at least 25. More magazines -- to use a tired metaphor -- means cutting the same pie into thinner slices.
2) Increased productivity: By at least one very important and legitimate measure -- output -- manufacturing is growing in both absolute dollars and as a percentage of the U.S. economy. However, it's doing so in large part because of productivity-boosting technology, which in turn -- as we all know -- has vastly reduced the number of people needed in the manufacturing sector. Fewer manufacturing employees means fewer people to receive MORE magazines. That makes it harder for advertisers to choose -- seemingly reinforcing their decision to spread marketing dollars across the wide range of specialty magazines.
3) The internet: Back in the day when magazines were fat, rich and happy, they represented the ONLY way that a marketer could reliably reach a large number of targeted prospects. Today, the internet provides all sorts of other ways to do that, such as webcasts and company websites and portal websites and Search Engine Optimization, etc. And marketers feel -- rightly in some cases and (I believe) not so in others -- that these methods are more justifiable than magazine advertising, because they deliver hard data about the impact of the marketing effort.
While marketing options have increased, I can assure you that marketing budgets have NOT. As a result, the same amount of marketing money -- already being spread among more magazines -- is also being spread among more marketing vehicles OTHER than magazine ads.
In the days you remember of fat magazines, our single largest competitor didn't even exist: Google.
Publishing is a difficult industry right now because of all these changes. And no publisher has yet really figured it out. We know our business models must change. Printing a magazine and mailing it is the single most costly activity that a publishing company can undertake; and it provides the infrastructure that makes all other business opportunities (such as this forum site) work. And yet, it's the thing we do that our advertisers LEAST want to pay for; it delivers much lower ROI for us than it once did.
So we change -- sometimes on a daily basis. I'm not whining about it, and I feel that American Machinist and Welding are farther along on the curve than most of our direct competitors. But that doesn't mean we've got it all figured out, either.
What it does mean is that your observation, while correct, doesn't necessarily reflect on the health of manufacturing or the magazines. American Machinist is as healthy as its been in years. So is the manufacturing sector. It's just that the picture of health in both these industries has changed.