Downtown Miami condominium sales slipped significantly in the last quarter of 2008, according to Bal Harbour consulting group Condo Vultures. Its recent survey said the closing rate on downtown condo sales dropped from 18 a day in the third quarter to five a day in the last three months of the year. About 22,000 condo units have been completed or remain under construction since 2003 — and by September 2008, about 17,300 had found buyers. That was a surprise to many analysts who believed the overbuilding was worse. Peter Zalewski, principal of Condo Vultures, said bulk sales would be the next phase of market activity.