Impact of “De Facto” Bridge Holidays

[EN] In this note, we focus on the significance of the effect of bridge-days, which are defined as extra day-offs between two successive official holidays or between a holiday and a weekend, on the seasonal adjustment process by taking industrial production (IP) as our laboratory. To this end, a bridge-day variable is constructed for Turkey. Additionally, we investigate whether eves of religious feasts and Republic Day which are currently assumed to be fully worked in by TurkStat should be treated as half-day holidays in seasonal adjustment. We find evidence that modifying the currently used working day variable in the way to incorporate these days improve the seasonal adjustment process significantly and hence, half day offs have an impact on IP. More importantly, results reveal that religious bridge-days are highly influential on IP, while any significant impact cannot be claimed for national bridge-days. As a matter of fact, bridge-day adjusted IP follows a remarkably more stable pattern compared to the officially announced data, providing evidence that bridge-day effect has been a major factor lying behind the recent volatile course of IP. Finally, we conclude that bridge days should be taken into account to remove bridge-day induced fluctuations and make proper inferences regarding the dynamics of working-day sensitive variables. [TR] Bu notta, birbirini takip eden iki resmi tatil veya bir resmi tatil ile hafta sonu arasinda kalan ve ek tatil yapilabilecek calisma gunu olarak tanimlanan kopru gunlerinin mevsimsellikten arindirma islemi uzerindeki etkisinin anlamliligi sanayi uretimi verisi uzerinde test edilmistir. Bu amacla, Turkiye icin kopru gunu degiskeni olusturulmustur. Ek olarak, TUIK tarafindan kullanilan calisma gunu degiskeninde is gunu olarak degerlendirilen dini bayramlar ve Cumhuriyet Bayrami’nin arife gunundeki yarim gunluk tatilin sanayi uretimine etkisi incelenmistir. Hali hazirda kullanilan calisma gunu degiskeni yarim gunluk arife gunu tatillerini icerecek sekilde revize edildiginde mevsimsellikten arindirma isleminin onemli olcude iyilestigine dair deliller bulunmustur. Daha onemli olarak, sonuclar dini bayramlar oncesi veya sonrasindaki kopru gunlerinin sanayi uretimi uzerinde belirgin bicimde etkide bulundugunu gosterirken, milli bayramlarla iliskili kopru gunlerinin istatistiksel olarak anlamli olmadigina isaret etmektedir. Kopru gunu etkisi arindirilmis sanayi uretiminin resmi istatistik kurumu tarafindan yayimlanan seriye oranla oldukca istikrarli bir seyir izlemesi, son donemde sanayi uretiminde gorulen dalgali seyrin altinda yatan onemli unsurlardan birinin kopru gunu etkisi olduguna yonelik bilgi saglamaktadir. Sonuc olarak, kopru gunu etkisinden kaynaklanan dalgalanmalari gidererek calisma gunu sayisina duyarli verilerin dinamiklerini daha dogru bir sekilde yorumlayabilmek icin kopru gunlerinin dikkate alinmasi gerektigi dusunulmektedir.