# Online calculators — 2009 statistics

Now that the AGU exposure-dating rush is over it is time to take a look at the online exposure age and erosion rate calculator usage statistics. Here are the yearly usage stats for the last four years of operation for the online calculators:

Year | Erosion rate calculations | Exposure age calculations | Total calculations |

2006 | 1367 | 8698 | 10065 |

2007 | 1919 | 29068 | 30987 |

2008 | 3565 | 55078 | 58643 |

2009 | 3104 | 41748 | 44852 |

These are compiled by counting each request for an individual exposure age or erosion rate calculation once. That is, if you submit 10 samples at the same time, 10 calculations are logged. The “test samples” accessible from the dropdown menu are not counted. Of course, 2009 is not quite over yet but the period between AGU and the end of the year is generally pretty slow.

Here are the monthly stats:

Some observations: first, after rapid growth in 2006-08, usage has stabilized and dropped off a bit in 2009. Why is this? For one thing, the number of calculations submitted to the exposure age calculator exceeds the global number of Be-10 and Al-26 AMS measurements by approximately an order of magnitude. So it is possible that most people have finished calculating exposure ages from old data, and the amount of calculator usage has fallen more into line with the amount of actual new data being generated. It’s also possible that we are seeing the effects of competition from a partially completed mirror site at the University of New Mexico or from the recently released “ACE” software. Overall, it seems most likely that the calculator usage has simply dropped into an equilibrium with the number of people who are actually interested in cosmogenic-nuclide geochemistry.

Second, exposure age calculations continue to be more than ten times as popular as erosion rate calculations. Why is this? One guess is that users interested in exposure dating would like to interpret exposure-age measurements at a much higher level of precision than users interested in erosion rates. For most applications of erosion-rate measurements to actual geologic problems, precision at the ~10% level is more than adequate. However, many users of exposure dating would like to make interpretations at a much higher level of precision, to answer questions like whether or not a moraine belongs to the Younger Dryas or the Antarctic Cold Reversal. Whether or not this is a good question to ask belongs to a different discussion, but I envision these users repeating their calculations with various different production rate calibration data sets, surface erosion rates, etc., to find out what effect these adjustments have on their results. Of course, I specifically constructed the online calculators to make this practice as inconvenient as possible — they are supposed to provide a standardized calculation method, not a means of production-rate shopping — but I suspect that this sort of activity accounts for a lot of repeated exposure age calculations. On the other hand, once an erosion-rate calculation is done once, it’s done and there’s no need to revisit it.