Türkiye'de kamu bütçesi tahminlerinin gerçekliği
Public budget forecasting accuracy in Türkiye
Yazar: BERAT KARA
Danışman: PROF. DR. NAGİHAN OKTAYER IŞIKLAR
İstanbul Üniversitesi / Sosyal Bilimler Enstitüsü / Maliye Ana Bilim Dalı
Derece: Doktora, 2024
Konu: Maliye = Finance
Dizin: Devlet bütçesi = Government budget ; Kamu maliyesi = Public finance ; Türk bütçe sistemi = Turkish public budgeting system

Özet:
Bütçe tahminleri, hükümetlerin mali politikalarını belirlemek ve kamu kaynaklarını etkin bir şekilde yönetmek açısından büyük öneme sahiptir. Ancak, bu tahminlerin doğruluğu her zaman sağlanamamakta, sıklıkla ciddi sapmalar ve hatalar ortaya çıkmaktadır. Bu hatalar, kamu maliyesinde dengesizliklere, bütçe açıklarının büyümesine, kamu borcunun artmasına ve ekonomik istikrarın bozulmasına neden olabilmektedir. Ayrıca, tahmin hataları, siyasi karar alma süreçlerinde yanıltıcı bilgiler sunarak, hükümetlerin seçmen desteğini kaybetmesine ve siyasi istikrarın zedelenmesine yol açabilmektedir.
Tahmin hatalarının kaynakları çeşitli olup, gelişmiş ve gelişmekte olan ekonomiler arasında farklılık göstermektedir. Gelişmiş ekonomilerde tahmin hataları genellikle dış şoklar, uluslararası krizler ve doğal afetler gibi beklenmedik olaylardan kaynaklanırken, gelişmekte olan ekonomilerde makroekonomik değişkenlerin yanlış öngörülmesi, hesaplama hataları ve politik belirsizlikler bu hataların başlıca nedenleri arasında yer almaktadır. 
Bu çalışma, Türkiye'deki bütçe tahmin hatalarını derinlemesine inceleyerek, bu hataların nedenlerini ve sonuçlarını ortaya koymayı amaçlamaktadır. Dört bölümden oluşan çalışmada, ilk olarak bütçe tahminlerinin kavramsal çerçevesi ve tahmin hatalarının nedenleri ele alınmıştır. İkinci bölümde, tahmin hatalarının nedenlerine ilişkin literatür taraması yapılmış, üçüncü bölümde ise Türkiye özelinde gider, gelir ve denge tahmin hatalarının boyutları ve nedenleri analiz edilmiştir.
Çalışmanın dördüncü bölümünde, 1984-2021 dönemi için toplam gelir, vergi gelir, gider ve bütçe dengesi tahmin hataları üzerine ekonometrik modeller geliştirilmiştir. Bu modellerde büyüme, enflasyon, cari açık gibi makroekonomik değişkenlerin yanı sıra, kriz dönemleri, koalisyon hükümetleri ve seçim yılları gibi politik değişkenler de değerlendirilmiştir. Analiz sonuçları, Türkiye'de enflasyon, geçmiş dönem tahmin hatası ve yapısal, kurumsal faktörlerin tahmin hatalarının temel belirleyicileri olduğunu göstermiştir. Buna karşın, kriz ve seçim dönemlerinin tahmin hataları üzerinde anlamlı bir etkisinin olmadığı tespit edilmiştir. Ayrıca, harcama tahmin hatalarında hükümet yapısının etkili olduğu ortaya konmuştur.
Sonuç olarak, Türkiye'de bütçe tahminlerinin doğruluğunu artırmak için enflasyon tahminlerinin dikkatle revize edilmesi, varsayımların titizlikle gözden geçirilmesi ve tahmin hazırlık süreçlerinde kurumsal faktörlerin etkisinin azaltılması gerekmektedir. Bu sayede, bütçe tahmin hatalarının azaltılması ve kamu maliyesinde daha sağlıklı kararların alınması mümkün olacaktır.

Abstract:
Budget forecasts are of critical importance for governments to anticipate their revenues and expenditures and to determine their fiscal policies. However, the accuracy of these forecasts is not always guaranteed, often resulting in forecast errors exceeding an acceptable level. These errors lead to incorrect decisions in public finance and policy-making processes, increased budget deficits, rising public debts, economic instability, loss of voter support, and endangerment of government stability.
The process of preparing forecasts for expenditure items, programs, and revenue sources is often fraught with errors, with the likelihood of these errors having a balancing effect and opening the door to realistic forecasts being quite low. Errors frequently compound each other, leading to more significant mistakes. Moreover, errors are often observed to repeat themselves over extended periods.
Forecast errors stem from various reasons. In advanced economies, the most common causes are external shocks, international economic crises, natural disasters, and unforeseen circumstances. In developing economies, incorrect anticipation of macroeconomic factors, miscalculation, erroneous assumptions, and political developments are seen as fundamental reasons.
The first step in rectifying errors is to quantify their dimensions and identify their causes. This process can facilitate the development of policy recommendations aimed at eliminating these causes. Indeed, this study is prepared with this goal in mind, focusing on the issue of forecast errors in Turkey.
The study comprises four sections. The first section elucidates the conceptual framework of budget forecasts, their importance, basic forecasting methods, reasons for forecast errors, their consequences, and alternative suggestions to prevent these errors. The second section includes a comprehensive literature review on the reasons for forecast errors. The third section focuses on forecast errors in Turkey, addressing the dimensions, causes, and ratios to GDP of errors in expenditure, revenue, and balance forecasts separately.
In the fourth and final section, a bias test for forecasts is conducted. While revenue, expenditure, and balance all appear to be consciously under-forecasted when looking at the numbers, econometrically, a bias toward under-forecasted expenditure forecasts only has been identified through the Holden-Peel test.
Following the bias test, four different models were constructed for the period 1984-2021 to econometrically analyze the causes of budget forecast errors in Turkey, covering total revenue, tax revenue, expenditure, and budget balance forecast errors. Due to issues of autocorrelation and unit root among the data, the Prais-Winsten regression was chosen as the method. Independent variables included growth, inflation, current account deficit, prior errors, as well as dummy variables for crisis periods, coalition government periods, and election years. Lagged versions of inflation and the current account deficit were also included in the models.
The total revenue model found that an increase in current-year growth, current-year inflation, and an increase in prior error all increase the forecast error. However, an increase in prior inflation rate decreases the forecast error. This last effect was not observed in the tax revenue forecast error model, although changes were observed in the impact of growth, inflation, and prior error.
According to the expenditure model, an increase in current-year inflation and current account deficit increases the forecast error, while an increase in prior inflation and forecast error decreases the forecast error. Additionally, expenditure forecasts during coalition periods were found to be more erroneous compared to single-party government periods.
Finally, in the balance model, an increase in the current account deficit led to an increase in the balance forecast error, while an increase in prior current account deficit and balance forecast error led to a decrease. However, structural, institutional, and technical factors in Turkey make it impossible to analyze the causes of balance forecast errors, as detailed in the third section of the study.
In conclusion, through econometric models, inflation, prior forecast errors, and structural, institutional, and technical factors were identified as the primary factors explaining forecast errors in Turkey. Crisis and election periods were found not to influence forecast errors. Another political variable, government structure, was found to only have an increasing effect on expenditure forecast errors. Therefore, efforts must be made in Turkey to increase the realism of budget forecasts by addressing these factors and exercising due diligence.
Firstly, in the preparation process, realistic inflation must be estimated, and budget forecasts should be prepared considering this estimation. It is not possible for each institution preparing forecasts to independently estimate inflation. This requires substantial data and technical expertise. It may be considered a solution for an institution with these capabilities to prepare an inflation forecast monthly and share it with public institutions, or to use the Central Bank's market participant survey. However, considering the length of the budget preparation process in Turkey and its top-down approach, forecasts must be revised at each stage considering new inflation expectations. 
Secondly, those preparing forecasts must review their assumptions at each forecasting period to avoid assumption drag. Assumption drag can stem from institutional identity, political trends, or the government's economic-political program. These factors are economic targets. However, when preparing the budget, there must be a full awareness of the difference between economic targets and forecasts. Factors underlying prior assumptions should be reevaluated, and alignment between economic targets and forecasts must be successfully achieved. Otherwise, the budget will be nothing more than a document containing economic targets.