add startup attribute: lifetimeUserValue

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need actions to update it, but could have it default to a min value > 0

TODO:

• [ ] calculate Cost of Customer Acquisition (#35)

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https://blog.kissmetrics.com/how-to-calculate-lifetime-value/ http://customerlifetimevalue.co/ http://www.entrepreneur.com/article/224153

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The input needed is: – the average yearly pledged donation per donor, (D) – the attrition rate year over year, for each year (A1),(A2) etc. (or their good twins, the Retention Rates (1-A1) etc…) Let’s try to do the calculation on a yearly basis, on a period of 3 years. We start, of course, from the yearly donation (D). We could be tempted now, to get the first year income, to multiply D(A1). But there is a problem with that: we are overestimating the attrition, assuming that all the donors leave at the beginning of the year. That’s not always the case, and if you have a lot of monthly or quarterly donors (like my organization does), also those had the time to make some donations before you lost them. My favorite way to make up for that is to use not the retention itself, but its square root (that’s (1-A1)^(1/2) ), to simulate an attrition that happens through the year at a constant “month by month” rate. The formula becomes (): 1st year LTV: D((1-A1)^(1/2)) 2nd year LTV: D(1-A1)((1-A2)^(1/2)) 3rd year LTV: D(1-A1)(1-A2)((1-A3)^(1/2)) 3 years gross Average LTV per sign-up = (1st year LTV)+(2nd year LTV)+(3rd year LTV)

http://101fundraising.org/2011/11/the-almost-magic-formula-of-lifetime-value-estimation/