Here’s a puzzle: Why does Nintendo (NTDOY.PK) expect dramatically fewer software titles to sell for its Wii and DS game machines this year?

This morning, Tokyo time, the company announced results for its fiscal year ended in March that were a little bit better than expected thanks to strength the Japanese Yen, turning in 1.8 trillion Yen in revenue ($18 billion, roughty) and 555 billion in operating profit. But for the current year, the company forecast sales to be flat, at 1.8 trillion, which is in line with estimates, but profit of 490 billion Yen, which is short of Street estimates for about 517 billion.

Nintendo says that’s because it will see a sharp decline in software titles for the DS, and software, of course, carries higher profit margins.

That’s not realistic, says Michael Pachter, who follows the company for Wedbush Morgan, in a phone call I had with him this afternoon. If the company expects to see sales of the Wii and DS remain roughly flat, it doesn’t make sense that software sales would be either flat or declining, says Pachter. That’s because the company sells, on average, 4 game titles for every Wii and 2 titles for every DS machine sold.

Nintendo’s predictions suggest those “tie ratios,” in industry jargon, will rapidly disintegrate, by 30% or so this year, something Pachter says has never happened in the history of video game software sales. Pachter calls the forecast “ridiculous,” though he’s trimming his own forecast for software sales slightly, to give the company some credit. Pachter thinks Nintendo is probably just low-balling numbers to beat at the end of the year.

Sure, it’s possible the company knows something it’s not fully described, like a dramatic fall-off in the number of games people buy with each new machine. If that were to turn out to be the case this year, it would be an extraordinary event for the industry, and bad sign for software makers such as Electronic Arts (ERTS).

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I sent Pachter an email about this - I don't disagree that the Wii SW forecast of 220m looks very beatable, but all the same a dip in game purchasing from 4.05 to 2.9 of the average game purchaser is in line with historical drops seen by machines ranging from GBA to PS1 to PS2 to DS over the last 15 years. Curious to see what he says.