the business concern with the average number of employees of each affiliate. § 121.106(b)(4)(i). If a concern has acquired an affiliate or been acquired as an affiliate during the applicable period of measurement or before the date on which it self-certified as small, the employees counted in determining size status include the employees of the acquired or acquiring concern. Furthermore, this aggregation applies for the entire period of measurement, not just the period after the affiliation arose. The employees of a former affiliate are not counted if affiliation ceased before the date used for determining size. § 121.106(b)(4)(ii). This exclusion of employees of a former affiliate applies during the entire period of measurement, rather than only for the period after which affiliation ceased. Affiliates and control Small business concerns as defined by federal regulations for the purposes of receiving small-entity discounts on patent fees may have a maximum of 500 employees, including affiliates. Thus, a business concern that might otherwise qualify for small-entity status might be disqualified if it is affiliated with one or more other business concerns that cumulatively have more than 500 employees. Affiliation is determined under a control test. Concerns are "affiliates" of each other for the purposes of 13 C.F.R. § 121.802(a) when one concern controls or has the power to control the other, or a third party or parties controls or has the power to control both. 13 C.F.R. § 121.103(a)(1). It does not matter whether control is exercised, so long as the power to control exists. The test for determining control takes in account ownership, management, previous relationships with or ties to another concern, and contractual relationships. § 121.103(a)(2). The federal regulations that describe control set out a number of circumstances where control obviously exists, as where one entity owns more than 50% of the stock in another entity, § 121.103(c)(1), or where one or more officers, directors, managing members, or partners who control the board of directors and/or management of one concern also control the board of directors or management of one or more other concerns, § 121.103(e). There are also a number of "safe-harbor" exceptions to affiliation coverage found in 13 C.F.R. § 121.103(b), mostly involving ownership by certain kinds of investment companies, venture capital operating companies, Indian tribes, § 501(c) nonprofits like charitable trusts, foundations, endowments, etc. If the assignee of a patent application has difficulty determining for itself whether it