Bank of Japan Rate Hike

The BOJ raised the discount rate from 0.1 to 0.4% and provided guidance that rate increases would not be consecutive. This was less contractionary than anticipated and the yen fell against the dollar. This move was largely symbolic. The BOJ members wanted to validate the recent (though modest) growth in the Japanese economy, but also did not want to contribute to any slowdown that might be triggered by the U.S. Fed's rate increases on the other side of the Pacific. These central planners do not really know what they are doing. It's not an exact science. Why not let the market (even if it is somewhat inefficient) determine interest rates?