PDAs are moving toward irrelevance, a new study by In-Stat released this week says.

Other studies in the last two years have shown flat sales for PDAs, the new study says the devices are entering a stage of serious decline. In-Stat reported that PDA shipments in 2004 were only 8.7 million, compared to 10 million in 2003.

The study predicted a negative annual growth rate of 21.5 percent through 2009. After that time, PDAs will be sold only for specific vertical markets, according to the study. As a result, In-Stat said, the PDA will soon stop being considered a major product segment.

The report attributed the decline of PDAs to increased sales of devices such as smartphones and portable media players, which it described as a "natural evolution" of the PDA. It said the trend will accelerate by the end of 2005, in which the study predicted the price of smartphones to decline significantly.

The report also suggested that PDA vendors will add cellular access, Wi-Fi and Bluetooth to their devices in order to compete.