3.6 Impulse Response Functions using Vector Autoregressive (VAR) Model
For analyzing the effect of fiscal shocks of government spending and taxes on debt-to-GDP ratio and other
macro-economic variables i.e. Output, interest rate, private consumption and exchange rate are estimated by
unrestricted Vector Autoregressive (VAR) model. The benefit of the methodology is that it allows estimating
small number of parameters and it does not enforce any type of restrictions on the economy. The VAR models
are characterized without any prior distribution between endogenous and exogenous variables. To analyze the
effect of fiscal shocks and government spending charges, methodology suggested by Blanchard and Perotti (2007) and Favero and Giavazzi (20007) is adopted for data of Pakistan for period 1971-2008.
The two VAR models are estimated, one includes government spending, output, private consumption, interest
rate, exchange rate and debt. The other model takes revenues instead of government spending while other
variables remain the same. The lag length of VAR selected three based on Akikia information Criteria (AIC)
and Schwartz Bayesian Criterion (SBC). The first model also replaces debt and use tax, as VAR methodology
reveals the possibility of different results in different cases. Figure 1 indicates the impulse response function
using VAR model that gives an evidence of fiscal contraction. In figure 2, the impulse response functions are
displayed when tax-to-GDP ratio is included. The tax shows a positive response towards government
spending. The positive response of expansionary shock towards tax and negative response towards debt seems
to indicate that increased tax revenue signals a reduction in future government obligations and suggests a
positive wealth effect. On the other side, an increased in public debt causes a decrease in the present value of
future revenues and reduced present consumption.
Figure 3 indicates an impulse response function using VAR model, introducing government revenue shock on
macro-variable. The impulse response shows revenue shock has negative impact on output and exchange rate
while has positive impact on consumption interest rate and debt. It implies that decreased revenue tends to
impact the output of an economy and reduce it. As a result of the reduced output, the economy will have to
import the goods which will no doubt negatively impacts the exchange rate and it will be depreciated. The
deceased revenue will result in increase debt as government will finance its expenses through debt in case of
revenue shock.