Like many people who spent their careers putting mostly black ink on white paper so it could be thrown on people’s porches at 5 a.m., I have been worrying about the future of independent nail salon insurance and newspapers. Most of the content newspapers provide is available free online and many of our best advertisers have found they can reach their best customers more efficiently using lower-cost, Web-based alternatives.

One of the essential facts newspaper ad people never talk about is the inherent inefficiency in newspaper advertising — and that this inefficiency is what drives profitability. In fact, the old Newspaper Advertising Bureau created a clever marketing name for the phenomenon — The Thin Market Concept — and used it to get customers to buy more ads.

Let me try an example using a make-believe newspaper with 250,000 circulation and 50% penetration, in a market of 500,000 homes.

The Thin Market Concept held that on any given day, about 3% of the households in a market wanted to buy a new refrigerator. If the newspaper charges $6,000 for a full-page ad for refrigerators, the cost of reaching each household is about 2.4 cents.

But the cost of reaching families that are actually in the market for a refrigerator is much higher. There are 15,000 homes in the market for a refrigerator and the newspaper, with that 50% penetration, reaches half — 7,500 — at a cost of about 80 cents per view by households ready to buy.

Fortunately for newspapers no one knows which households are ready to buy, so appliance dealers have no choice but to pay the newspaper the full $6,000 for ads.

The Web world turns this model on its head. Almost no rational person looks at online ads for refrigerators unless they are actively planning to buy one, so very little money gets wasted delivering ads to households who are presently happy with their cold storage. Even if the cost per view is many times that of newspapers, the total revenue is much less than that generated by the newspaper ad.

One response would be for newspapers to charge more per view; but, again, the way the Web works makes that pretty much impossible. One factor that allowed newspapers to hold 30% margins for so long was that cost of entry kept out competition. The infrastructure and overhead required to start or maintain a newspaper meant almost no market could support more than one general-circulation daily.

But that is not the case with the Web. Anyone with a decent off-the-shelf computer and software can build a Web site and start selling ads. Add commission-only salespeople, throw in a few bucks to register with the major search engines, and you are in full competition with the daily newspaper Web site, which has to support much higher overhead to deliver the news.

Another problem with newspaper Web sites: Many of their users live far from that local appliance store. For example, I read one print newspaper a day — the San Jose (Calif.) Mercury News — but I have 14 dailies in 9 states and two countries bookmarked in my Web browser. Although these newspapers are probably glad I use their Web sites, I am generally useless to their advertisers.

Most of what I have written here deals with the future of ads from newspapers’ best customers: large retailers and car dealers. But the one-to-one marketing nature of the Web also threatens the traditional readership value of in-column, private-party classified ads.

Here is an example: Last fall, I sold my 1962 Chevy Impala SuperSport Convertible. The only place I advertised the car was on craigslist.org — a free service that allows nearly unlimited text and up to four pictures. I posted the car at about 7 p. m. on a Wednesday. I did not list a phone number, my real name, or any contact information beyond an e-mail account I set up for this purpose.

By 10 p. m. the same night I had four e-mail responses, and ultimately 15 people e-mailed me about the car. There were two inquires from New Zealand. I got four offers and eventually sold the car for a couple of grand less than what I had in it. In the classic car world, this was a very good outcome.

My sales costs were exactly zero. In the days before the Internet, I would have run ads in newspapers and classic car publications. Multiply my experience by however many thousand a day, and the loss of classified revenue and readership from private parties is huge.

I wish I had some solutions to put forth, and I know there are very smart folks at individual newspapers and corporate headquarters working on these issues. My good friends at Knight Ridder send me a pension check every month — and I really want that to continue.