More than a quarter of General Motors Corp.’s hourly workers are expected to leave by the summer as a result of a recent buyout and retirement offer, the company announced today amid reports that Chairman and CEO Rick Wagoner will announce additional restructuring measures at its annual meeting next week.

GM said 19,000 of its 73,000 hourly workers have signed up for buyouts and retirement offers, GM announced this afternoon. Workers will be expected to leave by July.

While the number leaving is far higher than that of a similar program at Ford Motor Co. earlier this year, it is a bit below the number GM targeted under its special attrition program offers, also called the SAP.

“We had hoped that 20-25,000 would take the SAP at GM – setting up at least 12,000 hires this fall,” said Sean McAlinden, chief economist at the Center for Automotive Research in Ann Arbor. “I think GM assumed this also. So GM is much closer to its target than Ford.”

GM still has the capacity to build 1.7 million of its largest vehicles, from Escalades to Silverados, in North America, McAlinden said. “They probably only need 1 million units at most due to the structural change in the market. … So, we worry. Pontiac East, Flint Truck & Bus, they are all at risk.”

GM already announced this week that it is speeding up the elimination of a shift each at those pickup plants, even though they had been down for weeks because of the UAW’s strike against American Axle & Manufacturing Inc., which supplies those factories. The latest announcements leave them each with just one shift. It is considered inefficient and costly to operate plants with just one shift.

The workers are paying the price for the ratification of the lame contracts that the auto industry gave them.  The Workers need to be more protected and their unions are failing them in the category.