Car production data may cause some eyes to glaze over, but the numbers are closely followed in the auto industry.

Electric-car maker Tesla Motors doesn't report its exact sales, nor its precise production, so a cottage industry has sprung up to track its alleged production.

MORE: Tesla's Next Electric Car Line: Roundup Of What We Know Now

Among other things, at its Detroit Auto Show press conference yesterday, Tesla executives said the company had delivered "almost 6,900 cars" during the fourth quarter of 2013.

That was roughly 20 percent higher than the guidance Tesla had provided on an October conference call to discuss its third-quarter financial results.

Tesla Motors stand at 2014 Detroit Auto Show

Tesla Motors stand at 2014 Detroit Auto Show

And it's a sign that the company is continuing to streamline its production process, removing bottlenecks and smoothing the steady flow of components into its plant in Fremont, California.

While Tesla has not said how many of those 6,900 cars were sold in the United States--we would expect to learn that next month on its next conference call--the company likely sold between 18,000 and 20,000 Model S cars in the U.S. during 2013.

Added to that are about 2,600 sold in 2012, plus several thousand more delivered to European buyers starting last August.

A long thread recording Tesla Model S serial numbers was recently removed by its creator from the Tesla Motors Club forum because, he said, financial analysts were using it for purposes he wasn't comfortable with, as well as calling to interrogate him about the meaning of the data.

Still, Tesla itself tends to tease its numbers. On a slide shown during the company's press conference yesterday, the following bullet point appeared: "More than 25,000 Model S on the road today."

Adding in the cars in transit to Europe and now China--the company expects its first deliveries there "in a few weeks," according to Tesla vice president of worldwide sales and service Jerome Guillen--the company would likely be approaching 30,000 Model S cars built altogether.

Jerome Guillen and Diarmuid O'Connell of Tesla Motors, press conference at 2014 Detroit Auto Show

Jerome Guillen and Diarmuid O'Connell of Tesla Motors, press conference at 2014 Detroit Auto Show

The simplest of reportorial methods gave us more information: We looked at the serial numbers on the two Model S cars on display in Detroit.

They were, respectively, 0027945 and 0028319.

Even if those cars were fresh off the line and newly delivered, they were likely one or two weeks old.

Assuming they were more likely a month old--and Tesla continues to crank them out at a rate of "more than 600 cars/week"--the company has likely built its 30,000th Model S already. If it hasn't, that car will roll off the production lines any day now.

Which certainly sets Tesla Motors ahead of the unfortunate Fisker Automotive, the other startup maker of a pricey, striking, plug-in vehicle.

That company apparently made 2,000 or so of its Fisker Karma range-extended electric luxury sedans before production ended; whether more will appear is an entirely different story.

Meanwhile, in about 18 months, Tesla has built as many cars as Chevrolet sold Volts in the U.S. in its first two years on sale.

The comparison's not exact, of course, but it's a remarkable achievement for a company that many--including a few of its suppliers--felt might be able to make 5,000 cars over the lifetime of the Model S.


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