Hi Mr. Hill, thanks for your comment.  Unfortunately, information is often manipulated either unintentionally through ignorance or other intent.  To compare apples to apples, lighting needs to be compared on the basis of effective light power (lumens) per watt of electrical energy.  I suspect that the city installed new LED lights have lower lumen output and achieve their savings from being dimmer rather than more efficient.  In other words, the energy savings could have been equally achieved by lowering the wattage of the sodium lamps.  This is speculation based on typical data manipulation I see, but it might be interesting to ask the city to compare the lumen output of the sodium versus LED lamps.