Luno

I guess I haven't been a good blogger. I was busy being a good partner and parent. Luno is almost 4 months old.

post office statistics

Did you know that there have been a few times in the past when the cost of mailing a letter has actually decreased?

Historical USPS statistics

Yes, apparently the cost of mailing a letter decreased from 3 cents to 2 cents (per once) in 1919. That translates to approximately a 3.44% yearly increase to the current value of 42 cents. From the 33 cent cost in 1999 the increase has only been 2.5%. Can we assume from this that the cost of mailing letters has decreased? Now that we're getting close to a state of deflation, will the USPS lower prices again? Well, apparently that's not on their plan given that their financial situation is not very healthy. What they are considering is cutting delivery back to 5 days a week.

The number of delivery days doesn't seem to me like a big deal... assuming the number of days for the letter to get there remains unchanged.

Pregnancy Duration

Nicole and I were talking about pregnancy duration, and while we knew that it was on average around 280 days (So says wikipedia), we wanted something more significant, so we dug around to see what we could find.

Duration of human singleton pregnancy. A population-based study. (Bergsjø P, Denman DW 3rd, Hoffman HJ, Meirik O. 1990) Seems to be a good source of information:

In cases of reliable menstrual dates, the average duration from LMP to vaginal birth was 282 days (median), 281 days (mean) and 283 days (mode), remaining constant over the years of study. One standard deviation of the mean was approximately 13 days, varying slightly with age and parity. Ten per cent of these women gave birth post term (past 294 days).

There are also some stats from Evaluation of ultrasound-estimated date of delivery in 17 450 spontaneous singleton births: do we need to modify Naegele's rule? (T. H. Nguyen, T. Larsen, G. Engholm, H. Møller). Naegele's rule is a simple method for calculating the due date.

Here is a probability breakdown per week. This assumes a standard deviation of 13 and a normal distribution. You might need to read the article for more "exact" estimates. Take this with a grain of salt as this might not apply to all pregnancies. Also, just estimating the due date might be prone to error, so using a statistic based around this will depend on the accuracy of the estimate.