Malone acknowledges the difficulty of accurately measuring open source PBX use. The software can be downloaded anonymously with no way to know if it is ever put into a live business network, he says.

The open source study is the most massive one his firm has undertaken in 30 years. It relied on using raw download numbers plugged into an analysis model built based on responses the firm got from those surveyed as one predictor of the market.

Malone says that within three weeks he will have complete 2008 PBX sales data provided by manufacturers to plug into his calculations that will result in refined 2009 projections.