One in two small and midsize businesses (SMBs) have no recovery plan in the event of a network outage, data loss, or other IT disaster, according to a study released Tuesday by Symantec.

That represents an increase from a similar study Symantec conducted a year ago, when 47% had no program in place. Small businesses — defined in the report as firms with between 5 and 99 workers — may be at particular risk: 57% have no disaster recovery plan. 47% of midsize companies with between 100 and 1,000 employees didn’t have a recovery process in place.

Of the firms without a disaster recovery plan, 41% said it had never occurred to them. 36% said they intend to implement one within the next six months. More than half (52%) said they don’t think computer systems are critical to business — that translates roughly to one in four of all of the businesses polled.

“This is probably the most shocking revelation of the survey,” Laroche said. “That’s pretty alarming.”

Symantec’s 2011 SMB Disaster Preparedness Survey included 1,288 businesses worldwide with between 5 and 1,000 employees — as well as 552 customers of those companies — across a broad range of industries. A “disaster” could be anything that causes an outage or data loss, whether natural or human-made. The new findings arrive in spite of a different Symantec report, published in June, that showed SMBs are increasingly fearful of online threats and data loss.

The businesses polled experienced on average six outages during 2010, with the top reasons given including cyberattacks, power failures, and natural disasters.

Those outages are expensive, according to Symantec’s data, to the tune of $12,500 vaporized from the business’ bottom line per day of downtime. Customers of SMBs also feel the pain: Outages at their SMB vendors cost them $10,000 per day, and 44% said they have had a smaller vendor temporarily shut down because of a technology failure. 29% of the customers in the study said they have lost “some” or “a lot of” data owing to a vendor’s disaster.