The complexity of mowing the lawn

20/12/2011 § 8 Comments

We sometimes underestimate the complexity of decisions that include intertemporal components and stochastic elements. That was my thought as I forced my push mower through lank, moist grass this weekend. I couldn’t be bothered to mow the lawn two weeks ago when the weather was fine, and I was paying the price for my laziness.

It shouldn’t be hard to optimise my intertemporal utility with respect to mowing. I want to minimise the effort to keep the lawn respectable-ish and usable. Effort is a combination of number of mowing occasions and difficulty of mowing. It’s just min(effort) = min(f(occasions, difficulty)).

The problem is the stochastic nature of both occasions and difficulty.

  • Occasions is a function of my schedule and my family’s schedule. I can’t always be at home when the right mowing occasion arises. It is also weather-dependent: I can’t mow in the rain or shortly afterward.  That means I’m trying to minimise a more complex function: min(f(occasions|schedules, weather; difficulty).
  • Difficulty is also variable. Partly, it is a function of the recent weather and my mowing technology. I bought a push mower several years ago because my lawn, my garage, and my children were small. With a power mower, the difficulty function would be different. I could more easily mow wet grass, and I could let the grass get longer. Difficulty is also a cumulative function. It isn’t just rain yesterday or today that increases the difficulty. It is the cumulative moisture and warmth that encourages growth. The function is closer to min(f(occasions|schedules, weather; difficulty|weather, technology)).

Of course, the same weather that shrinks the number of available occasions increases the difficulty, so there’s a non-linear, reinforcing effect. Add to that the role of expectations. I have poorly anchored expectations for Wellington weather, having lived here only a year. My priors from other climates are reasonably poor for predicting rain patterns and grass growth here. I end up with Shacklian surprise.

The good news is that I didn’t feel like I’d made the wrong decision two weeks ago. That is, even with perfect foresight I still would have chosen to be lazy. However, my total utility was lower than expected.

If I were really risk-averse, I could participate in the lawn mowing insurance market and reduce the variability of my intertemporal utility. I could just hire a gardener.



§ 8 Responses to The complexity of mowing the lawn

  • Thorsten Heitzmann says:

    Well, I started with a push-mower (but was too lazy and the ground is not flat enough), then moved to a motorized mower (but still the grass grows too fast) and now I found the perfect solution:
    Not in reinsurance, but in an “auto-mower” – even my wife is happy now!

  • You don’t have a gardener?! I have to conclude that you enjoy mowing and the angst that comes with the calculus you describe.

    When we bought our place in ’05, it had roses. We didn’t know what to do with roses. So we hired a gardener. We don’t have to think about the roses. Or the lawn. Or the plants around the house. If the lawn gets long between the gardener’s monthly visits, I may mow. But the Council’s ban on watering means that I don’t have to do that too much.

    I still need to outsource house cleaning.

    • JC says:

      Buy a goat..

      That takes care of the lawn, the roses, the washing, and the Jehovahs.


  • Bill says:

    @Thorsten – ah, the technological solution! Also an option. My lawn is too small for a ride-on mower, however. I would look silly.

    @ Eric – I wouldn’t say I enjoy mowing, but it does reduce my purchases of gym membership. I do enjoy tending roses. Hooray for preference heterogeneity!

  • jz says:

    This decision reminds me of Arthur Grimes’ discusssion of real options: perhaps, given the stochastic nature of the weather, the value in delaying really was that high.

    • Bill says:

      Ex ante, you’re probably right. Ex post, the grass was really long and far too wet to mow properly.

  • lawn says:

    Anyone know how much gardeners typically cost? I love mowing the lawn, but flowers aren’t really my forte….thanks!

  • The key to simply mowing is twofold. Buy the widest and most powerful mower you can afford, and mower as often as possible. At least once a week preferably twice. What makes mowing a pain is having to empty the bag all the time.

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