By George Polgar

PHILADELPHIA (CBS) – As sunny summer gives way to the autumn chill, real convertible fans swear it’s the best time to go for a top-down spin.

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Based on sales figures, the sun may be setting for convertibles altogether. In 2004 top-down models comprised 5 percent of the total US car market, down to just 1.2 percent this year. And the trend is international, with convertible sales off 44 percent worldwide in the past decade.

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Convertible popularity has often been associated with economic downturns, as buyers opt for practicality. In the economic malaise of the late 1970’s convertibles became all but extinct, and then roared back to the highest popularity ever in the 80’s and 90’s.

In addition to the economy, the boomers who embraced the carefree convertible lifestyle are now aging, while younger buyers prefer SUVs with an expansive glass sunroof.

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And yet recent test-drives of the exciting new BMW 428i convertible and the performance value packed Nissan Z Roadster not only reaffirmed the inherent appeal of convertibles but really showcased how far they have come with one-touch convertible hardtops and performance and safety-oriented engineering and construction.