Barchart bar lengths not proportionate

When I use barchart (with default formatting options), I get bars whose
lengths/heights are not proportional to their value. For example:

http://drop.io/wbagm6s/asset/capture-png

Many of the values in this chart are 1; however, because the blue bars
extend to the left of the "0" tick mark, those bars appear to represent
higher numeric values. Is there a way to make the length of the bar
proportional to the data value, so that people looking at my chart are not
misled?