In Riddle v. Riddle (2005) 125 Cal.App.4th 1075, the husband was a commissioned salesman whose income fluctuated with the financial market, and the trial court based a support order on his latest two months of earnings. The appellate court held it had been "a manifest abuse of discretion to take so small a sliver of time to figure income that the determination essentially becomes arbitrary." (Id. at p. 1083.) Although the Riddle court declined to create a bright-line test, the court instructed on a reasonable method for determining average annual income: "While Family Code section 4055 is framed in terms of 'net monthly disposable income' (see 4055, subd. (a)), section 4060 defines that phrase in terms of 'dividing the annual net disposable income by 12' and section 4059 defines annual net disposable income in terms of 'annual gross income.' In short, there is a heavy emphasis on 12 months or 'annual' income as a benchmark for the calculation. Which is, come to think of it, only common sense anyway: The income tax laws which, like support orders, are focused on income, are also framed, not in terms of artificially truncated and therefore unrepresentative slices of time, but in terms of whole years." (Id. at pp. 1083-1084.)