@slotmachine,

The z-scaling of the largest bubble, depends on the z-scaling of the smallest bubble. If you have a reference dataPoint, which is considerably small compared to the remaining dataPoints, you can notice the actual difference in size among the dataPoints.

You can add a dummy/reference dataPoint and setting the color: "transparent", toolTipContent: null, will make the dummy dataPoint invisible/ inactive. Please take a look at this jsfiddle, which has a reference dataPoint and reads user’s data from external JSON.

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Priyanka M S
Team CanvasJS