A man walks into a tailor, orders a custom-made suit and then says he's bound by his own rules to only buy half of it. Sell the rest to someone else, he says.

That, essentially, is the conundrum facing S&P Dow Jones Indices, except that instead of a suit, it's designing a stock gauge to the specifications of the Bank of Japan.

The central bank wants to buy baskets of shares based on indexes that pick companies partly on whether they raise wages. Salaries are a key battleground in the BOJ's efforts to spur inflation, and firms have so far been hard to budge.