(concurring) :
On the record before us, I would have no reason to disturb the Board’s conclusion that petitioner had an independent employment relationship with the workers in question sufficient to subject it to the Act. It seems obvious that the World Bank elected not to maintain its office building itself, and that it looked to petitioner for the performance of these functions for a price. Petitioner had to recruit and supervise the requisite workers, and it appears to have been legally liable in the first instance to pay their wages, Social Security taxes, and so on. If the World Bank were the First National, there would be no doubt in my view that petitioner was subject to the Board’s jurisdiction.
But the World Bank is what it is, and I wonder whether the Board would assert jurisdiction over it if it had not contracted out its maintenance needs. If the Board would not, then I wonder whether petitioner, as an employer providing services similar to those supplied other exempted institutions and on similar terms, is not being treated differently to a degree that approaches the arbitrary. The joint employer concept, if *687applicable, would presumably mean that two persons are subject to the Act rather than one. It does not appear to me to imply that, if one of such two is an exempt institution, the other must invariably be treated as exempt also, unless the Board chooses to do so. But this is a choice the Board has apparently made on some occasions, and what we need to know from the Board is whether, or why, petitioner is being treated differently. It is this to which the Board needs to address itself, and it is for this purpose that I would remand.