Automotive industry analysts have openly wondered throughout 2014 if new vehicle sales still have room to run, and so far the answer is clear: yes. August's Seasonally Adjusted Annualized Rate, or SAAR, hit 17.5 million units, the strongest August performance in more than a decade and, if estimates hold true, September looks set to turn in a very strong performance as well. Here's a look at the estimates for September sales and a few factors to consider.

By the numbers
While September sales figures will almost certainly fail to top August, that's not something to worry about. Historically, new vehicle sales decline substantially after Labor Day, but indications so far are that this year's decline was much less significant than most years'.

J.D. Power and LMC Automotive estimate that the U.S. automotive industry's total SAAR for September will check in at 16.5 million units when all is said and done. That's much stronger than last year's September mark of 15.4 million units.

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Chart by author. Data source: Automotive News DataCenter. September 2014 data is estimated from J.D. Power information.

A more accurate measure of demand looks specifically at retail SAAR figures, rather than total SAAR. Fortunately, the end consumer is still shopping for new vehicles at a healthy clip, with retail SAAR climbing from 12.3 million units during last year's September to an estimated 13.5 million units this month.

"The strength in automotive sales is undeniable, as August sales performance was well above expectations and there is no evidence of a payback in September, suggesting that the auto recovery still has some legs," said Jeff Schuster, senior vice president of forecasting at LMC Automotive, in a press release. "On the heels of another increase in the 2014 expected volume, 2015 is expected to hit 16.7 million units with more upside potential than downside risk."

3 things to consider
The automotive industry can be tricky, and there are many variables to consider when dissecting monthly and annual sales figures. For instance, fleet sales to large companies can significantly inflate sales at random times. Fleet sales in September are expected to increase to 19% of total light-vehicle sales.

While that might lead some to believe September's estimated performance will be inflated by fleet sales, that's not the full story. You must consider the fact that during the previous two months, fleet sales of total light vehicles have been below 15% -- and those have still been two very strong selling months. When looking at sales in three-month chunks, fleet sales haven't been inflating overall monthly sales performances.

Another factor to keep in mind when analyzing monthly sales is the number of selling days. Sometimes there is a significant difference from year to year, which if left unaccounted for can skew comparisons. This September will have 24 selling days compared to 23 selling days during September 2013. When adjusted for the one-day difference, this September is still expected to churn out 5% more total vehicle sales -- a respectable, and more accurate, gain.

One last factor to keep in mind as we try to gauge the health of the automotive industry is vehicle inventory. At the end of August the industry's vehicle inventory was at a 56-day supply, according to J.D. Power. That was a decline from July's 61 days of inventory, and it remains below normal inventory levels. When industry inventory is held in check, it's a healthier scenario and there's less risk for incentive wars among automakers.

Ultimately, all of the factors and estimates point to a very strong retail and total September SAAR with no red flags in terms of excess vehicle inventory or inflated performance due to fleet sales. So far, despite industry analysts wondering how long new vehicle sales can push higher, sales don't appear to be slowing down anytime soon. 

Daniel Miller owns shares of Ford. The Motley Fool recommends and owns shares of Ford. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.