A comment in today’s Financial Times is by a former Morgan Stanley trader, Douglas Keenan, confirms a passing comment in the Economist, that Libor manipulation goes back for more than 15 years. In fact, this piece makes it clear that is the time frame exceeds 20 years. From the Financial Times:

In 1991, I had live trading screens that showed the Libor rates. In September of that year, on the third Wednesday, at 11 o’clock, I watched those screens to see where the futures contract [on three month Libor] should settle. Shortly afterwards, Liffe announced the contract settlement rate. Its rate was different from what had been shown on my screens, by a few hundredths of a per cent. As a result, I lost money. The amount was insignificant for me, but I believed that I had been defrauded and I complained to Liffe [ London International Financial Futures Exchange, which is where the contract traded]. Liffe explained that the settlement rate was not determined by what rates were actually in the market. Instead, the British Banker’s Association polled banks, asking them what the rates were. The highest and lowest quoted rates were discarded and the rest were averaged, giving the settlement rate. Liffe explained that, in doing this, they were adhering to the terms of the contract. I talked with some of my more experienced colleagues about this. They told me banks misreported the Libor rates in a way that would generally bring them profits. I had been unaware of that, as I was relatively new to financial trading. My naivety seemed to be humorous to my colleagues.

So consider what this tells us:

1. Libor manipulation was already recognized by market participants in 1991 as a common phenomenon. That implies it had been going on at least a few years before that 2. The manipulation appears to have more than occasionally been more than a single basis point (Keenan says here the effect was “several” basis points, which I take to be three or more)

Oh, an an additional tidbit: Bob Diamond was in Morgan Stanley London as of then, in charge of interest rate trading, which means his claim that he had found out about Libor manipulation at Barclays mere weeks before his Treasury Select testimony was bollocks.