Everyone gets their Christmas Bonus somehow

In Guyana, salaried employees traditionally receive a 13th month bonus-- the equivalent of one month's salary, paid as a bonus at the end of the calendar year. 

This bonus, combined with the rush to buy gifts and traditional holiday foods, creates a surge in demand which I'm told pushes prices in the market up in the days before Christmas. Eggs in particular have a reputation for becoming outlandishly expensive. 

I decided to see if the anecdotes shared by my colleagues were reflected in price data. They weren't. There is no seasonal uptick in Guyana's consumer price index in December. (There is some macro evidence of the bonuses: currency in circulation spikes in January.) 

Assuming my colleagues' stories of spiking market prices are correct, why is there no increase in the CPI in December? I can think of several reasons.

• First, not all vendors may raise prices. While many market sellers likely do, I saw no increase in the prices at the small supermarkets where I do most of my shopping. It is likely more costly for modern-style supermarkets to temporarily raise prices, both in terms of "menu costs" and customer loyalty. 
• Second, how much prices rise may vary by product, depending on the price elasticity of demand. The high demand at Christmas is predictable, so in theory, many suppliers could increase their stock without much increase in per unit cost. This might not be the case for locally produced perishable items like eggs, however. Chickens are unlikely to step up their laying in anticipation of Christmas baking needs. For these items, extra demand can have a dramatic effect on price. 
• Lastly, CPI statistics may simply not capture the temporary price spike. CPI data are based on weekly surveys of five markets, and monthly surveys of another 110 outlets such as supermarkets and gas stations. The monthly surveys are conducted on the 15th, so the price surge in the days before Christmas would not be picked up. The weekly surveys might capture it, though it depends on their timing. 

Despite my colleagues' warnings, I found myself running around on Christmas Eve doing last-minute shopping. None of the stores I visited seemed to have inflated pricing, and the only market purchase I made was a few vegetables from my regular vegetable lady, who charged me the normal prices. I did have one taxi driver who asked for twice the regular fare. There was a long line of empty taxis waiting for passengers, so I didn't have much trouble negotiating down to 150 percent of the normal price. I decided to give the driver a hard time, supply-sider style.  "I know that fuel prices are the same today as every other day. So why are taxis more expensive?" He laughed. "Everyone has to get there Christmas bonus somehow!" 

I didn't tell him that I'd paid all my taxis extra that day, even the ones who'd asked the regular price, even though there didn't seem to be a shortage of taxis. Maybe for a short time during the holidays, the market just doesn't clear. Or maybe we pay a little extra, and we buy a little extra holiday cheer.