Countrywide Home Loans reclaimed the top spot among issuers of Ginnie Mae mortgage-backed securities at the halfway point in 2001, although industry consolidation could create a new market leader in coming months. Countrywide finished 2000 as the top Ginnie Mae issuer, but slipped to second place after the first three months of this year. Through June, however, the California-based mortgage banker had issued $6.04 billion of the agency’s MBSs, garnering it 8.6 percent of the