Critically evaluate this economic commentary:

When it comes to measuring inflation, the average consumer can do a far better job than the economics experts…. Over the years I have been using a system which is infallible…. The Phindex [short for the Phillips index] merely requires you to divide the total dollar cost of a biweekly shopping trip by the number of brown paper bags into which the purchases are crammed. You thus arrive at the average cost per bagful.

When I started this system some 10 years ago, we would walk out of the store with about six bags of groceries costing approximately $30—or an average of $5 per bag…. On our most recent shopping trip, we emerged with nine bagsful of stuff and nonsense, totaling the staggering sum of $114…. [T]he Phindex shows a rise from the initial $5 to almost $13, a whopping 153 percent.