In Howard Johnson Co. v. Hotel Employees (1974) 417 U.S. 249, the court refused to bind a successor to an arbitration clause in its predecessor's collective bargaining agreement. The court repeated the rule that an employer who purchases all the assets of another employer is under no obligation to hire the latter's work force, and it repeated the caveat to this rule: refusing to hire them because of union membership or activity is an unfair labor practice in violation of 29 United States Code section 158(a)(3). (417 U.S. at p. 261, fn. 8.) In Howard Johnson the new employer hired only nine of its predecessor's employees and none of its supervisors. Although the basic nature of the business (a motel) was not changed, there was no "substantial continuity in the identity of the work force" (417 U.S. at p. 263), nor any assumption of the agreement to arbitrate. Consequently, the new employer was not a successor for purposes of a duty to arbitrate.