Abstract
This study analyses the public debt sustainability issue of 20 major Indian states using the Bohn framework for panel data from 2005–2006 to 2014–2015. It employs regular panel data estimation procedures and the penalized spline (p-spline) technique. The results indicate that the primary balance of state governments responds positively to high public debt, so debt policies are successful in sustaining the debt situation of Indian states as a whole. However, at the individual level, debt is sustainable only in 12 states; in 8 states, debt is unsustainable and so these states require corrective action. These findings may be useful to policymakers and other stakeholders to formulate appropriate strategies to improve the debt situation of Indian states.
Introduction
After the seminal contribution of Hamilton and Flavin (1986), several empirical studies have been conducted on the sustainability of public debt. Three empirical approaches have evolved over the traditional indicator approach. They are the: (a) unit root approach (Caporale, 1995; Trehan & Walsh, 1991; Uctum, Thurston & Uctum, 2006); (b) cointegration approach (Hakkio & Rush, 1991; Jha & Sharma, 2004); and (c) Bohn’s model-based approach (Abiad & Ostry, 2005; Bohn, 1998). In the first approach, the debt series needs to be a mean-reverting process, while in the second approach, the public revenue and public expenditure series need to be cointegrated. The Bohn model suggests that primary surplus relative to GDP is a positive and at least linearly rising function of the public debt-GDP ratio.
The economic intuition behind the Bohn approach is that if governments run into debt today, they have to take corrective actions in future by increasing the primary surplus, otherwise, public debt will not be sustainable (Greiner & Fincke, 2009). This model has been widely used to test whether public debt policies in different countries are sustainable or not (Abiad & Ostry, 2005; Fincke & Greiner, 2011; Greiner & Kauermann, 2008; Haber & Neck, 2006; Kaur, Mukherjee, Kumar & Ekka, 2014; Mahdavi, 2014). 1
The debt sustainability issue is relevant not only for national governments but also for sub-national governments (states) because in countries like India, both governments borrow to finance their deficits. During 2006–2007 and 2007–2008, the centre and states in India (combined) had a primary surplus of 1 per cent of GDP, but in the following year (2008–2009), the combined primary deficit was −3.25 per cent of GDP; in 2009–2010, it rose to −4.53 per cent. The combined debt also increased and reached 88 per cent of GDP (of which the centre’s alone was 61 per cent) in 2005–2006. The aggregated debt of all states rose from ₹11,477 billion in 2005–2006 to ₹27,038 billion in 2014–2015.
In the Indian context, studies, such as Rangarajan, Bhide and Pattnaik (1989), Moorthy, Singh and Dhal (2000) and Pattnaik, Misra and Prakash (2003), used the traditional indicators approach, which basically uses the popular Domar condition. 2 Studies, such as Buiter and Patel (1990) and Pradhan (2014), employed the unit root approach, while Jha and Sharma (2004) and Tronzano (2013) used the cointegration approach. Tiwari (2012), Kaur and Mukharjee (2012), Jose (2014) and Shastri and Sahrawat (2015) applied the Bohn framework. Only a limited attempt has been made to analyse the issue at the state level.
However, most of the studies have used the Domar condition (Dholakia, Mohan & Karan, 2004; Maurya, 2015; Misra & Khundrakpam, 2009; Rajaraman, Bhide & Pattnaik, 2005). Only Kaur et al. (2014) employ the Bohn framework and show that debt is sustainable for Indian states as a whole. But the question remains whether debt is sustainable for each Indian state, as the aggregate picture may hide specific individual status. Therefore, this study attempts to use the Bohn methodology for panel data to test whether debt is sustainable in 20 major Indian states from 2005–2006 to 2014–2015. It also uses the penalized spline (p-spline) estimation procedure to estimate the time-varying coefficients or reaction coefficients, showing how coefficients associated with the debt-GDP ratio evolve over time across states. 3
Thus, this study differs from past studies in the following two respects: (a) This is the first study using the Bohn model for panel data to test the sustainability of debt in 20 major Indian states, individually and provide the state-specific policy suggestions on whether a given debt policy of a state can go on or it needs to be changed; and (b) this is the first study employing the p-spline estimation procedure for a panel of Indian states to show that the reaction coefficient has not stayed constant, but varying across states and time. The rest of this study proceeds as follows. The first section provides a brief note on public debt scenario in India. The third section presents a brief review of literature. While the fourth section explains the data, the model and the variables used in this study, the fifth section presents and discusses the empirical results. The final section gives the policy implications and concluding remarks of the study.
Indian Public Debt Scenario
The Indian Constitution (1950) has provided for a two-tier system of government: the centre and states, each with separate tax powers and expenditure functions. As all mobile and buoyant taxes are assigned to the centre, the states generate their own revenues from less buoyant taxes (like state VAT) assigned to them and non-tax and non-debt capital receipts sources to meet their expenditure commitments. At the same time, states are assigned more expenditure functions than the centre. In the centre, the excess federal revenues relative to its responsibility and a corresponding deficit in states’ accounts where expenditures exceed revenues is referred to as the vertical fiscal gap (Rangarajan & Srivastava, 2008). Recognising this vertical imbalance, the Constitution provides for transfer mechanisms to transfer resources from the centre to the states in the form of tax devolution, grant-in aid and centrally sponsored schemes (Rao, 2005).
Both governments borrow if their revenues cannot meet their expenditure needs. The centre in general borrows from internal and external sources, 4 while states’ internal debts include market loans and bonds, ways and means advances from the central bank (the Reserve Bank of India, popularly known as the RBI), loans from banks and other institutions, provident funds, etc. States’ external debts are subject to a ceiling and approvals from the centre.
Centre, States and Combined Primary Balance and Public Debt Ratios, 2004–05 to 2015–16
Centre, States and Combined Primary Balance and Public Debt Ratios, 2004–05 to 2015–16
In India, three broad deficit measures are used—the revenue deficit (excess of revenue expenditures over revenue receipts), the fiscal deficit (primary deficit + interest payments = net borrowing) and the primary deficit (the excess of residual non-interest expenditures over total non-debt receipts). Since state governments have constraints on their borrowing sources, they face an inconsistency between their borrowing requirements and debt servicing, but have annual debt requirements in the form of interest obligations on accumulated debt. The extent of these commitments every year is reflected in the primary balance. It is basically the amount of borrowings that are required to meet expenses other than the interest payments (primary deficit) or the pressure of the government on the interest commitments on previous borrowings to borrow (primary surplus). Therefore, the primary balance is the source of all types of deficits and it improves or worsens the fiscal situation due to total debt requirements.
Governments face two types of motivations to expand their activities above trend levels: to minimise the impact or volatility of the cyclicality of growth and to finance their political agendas (Srivastava, 2012). Trends in the primary deficit relative to the GDP and public debt relative to GDP since Independence indicate the cyclical nature of the former and the secular upward nature of the later (Rangarajan & Srivastava, 2005). Since the second half of 1990s, there has been a sharp deterioration in the debt-deficit situation of both centre and states. To reduce debt to a sustainable level, the centre adopted a rule-based fiscal framework (FRBM) in 2003 and most states enacted FRBM rules in 2005–2007, 5 with some initial success. 6

The situation has worsened since the global slowdown in 2007–2008: fiscal consolidation has been completely reversed due to a combination of spending measures, soaring subsidy bills and fiscal stimulus packages in response to crises, etc. (Tiwari, 2012) (Table 1).
The initial minimal combined primary deficit became surplus in 2006–07 and 2007–08, mainly because of the FRBM Act and other fiscal consolidation measures like the debt swap scheme (in which the 12th Finance Commission allowed states to swap high-cost loans against open-market borrowings and small savings in 2002–04), and the debt write-off scheme (in which the 13th Finance Commission offered a full write-off if states had a zero revenue deficit in 2008–2009 on their debt repayment to the centre and a concession on their interest rate). However, after the global crisis, the combined primary deficit reached an alarming 4.53 per cent in 2009–10, of which the centre’s primary deficit alone was 3.17 per cent.
As most states managed to fulfil their FRBM norms, their debt-GSDP (gross state domestic product) ratios declined from 26.8 per cent in 2005–2006 to 20.8 per cent in 2015–2016 but remain over 25 per cent in seven states, including Jammu and Kashmir (54.9%), Himachal Pradesh (41.9%) and West Bengal (34.7%) (Figure 1). If the current trend continues, many states will undergo adverse conditions. As implementations of the Fifth and Sixth Pay Commission recommendations have increased the revenue deficits and debt positions of many states, the proposed Seventh Pay Commission recommendations may be expected to add fuel to the debt positions of many state governments (Kurian, 1999; Rajaraman et al., 2005). Further, the rolling out Goods and Service Tax (GST) may result in a revenue loss in some states, which will in turn affect their debt sustainability.
Given the above trends in debt, this study considers the period from 2004–2005 to 2014–2015 because this is the post-FRMB period as well as represents the fiscal control era (by 12th and 13th FCs). In addition, various socio-economic-political and dynamic factors emerged in this period. Debt is in fact an accumulation of fiscal deficit every year and so the recent trend on debt is more concern than the past trend.
Debt sustainability is maintained as long as debt does not accumulate at a rate far exceeding the government’s capacity to service it. Unsustainable debt levels can lead to major disruptions in economic activity and reorientation of priorities in an economy. There are three theoretical views on debt financing: the neoclassical view is that a fiscal deficit is detrimental to investment and economic growth, while the Keynesian stance is that a deficit has a growth-stimulating effect. Debt does not pose a problem if the governments run into debt in the home country, as resources are not lost and public deficits imply a reallocation of resources from tax payers to bond holders (Greiner & Fincke, 2009). The third view, the Classical Ricardian equivalence theorem asserts that fiscal deficits do not matter, except for smoothing adjustments to expenditure or revenue shocks. Their stance is that budget deficits today will require higher taxes in future if government cuts taxes without changing present or future public spending. Given that households are forward looking, they realise they need to pay higher taxes in future so their total tax burden remains unchanged, and they reduce their consumption and increase savings to meet their future tax burden. This theorem is based on the inter-temporal budget constraint of the government and on the permanent income hypothesis. Thus, there is no consensus among economists on whether deficit financing is good, bad or neutral (Rangarajan & Srivastava, 2005).
Since the Keynesian view dominated in the 1970s, the public debt rose considerably over the period and was often was even higher than the GDP growth in many countries, so that the ratio of public debt to GDP increased, too. This raised the question of sustainability of the time-path of public debt, 7 and several studies emerged to address this question starting with the seminal paper by Hamilton and Flavin (1986). Earlier studies had mostly employed the Domar (1944) condition, according to which three conditions emerge from the basic debt accumulation equation:
where dt is the debt-GDP ratio in period t; g is the nominal economic growth rate; i is the nominal interest rate; p is the primary deficit relative to GDP in period t; and the conditions are gt = it, gtt and gtt. Fiscal policy is unsustainable when gt= it or gtt, because dt grows linearly when gt =itand explosively when gt t. Debt is sustainable when gtt. The last condition is considered a necessary condition for sustainability, based on the assumption that the faster income grows the lighter will be the burden of debt.
This approach was extended with additional indicators (growth, liquidity, credit worthiness, fiscal burden, fiscal space, etc.) and renamed the ‘indicator approach’ (Blanchard, Chouraqui, Hagemann & Sartor, 1990; Kaur et al., 2014; Maurya, 2015; Misra & Khundrakpam, 2009; Pattnaik et al., 2003; Rajaraman et al., 2005). As it applied the condition every year and is not sufficient enough to validate whether the inter-temporal budget of the government is satisfied or not, many proposed an econometric or statistical validation to substantiate the sustainability conditions.
Hamilton and Flavin (1986) carried out the first study using the unit root test to check whether the public debt series (Dt) in the USA is stationary or not, followed by Trehan and Walsh (1991). They use augmented Dickey–Fuller (ADF) statistics to test the hypothesis that the given series is non-stationary (H0) against the alternative hypothesis that it is stationary (Ha). Trehan and Walsh (1991) used another test to analyse whether a quasi-difference of public debt (Dt – vDt–1) with 0 ≤ v < 1 + r (where r is the interest rate) is stationary, and whether public debt and primary surpluses (St) are cointegrated. If government debt is quasi-difference stationary and public debt and primary surpluses are cointegrated, then the public debt is sustainable (Greiner & Fincke, 2009). (See Afonso (2005) for a brief survey of studies employing these procedures.) 8
These approaches have been criticised for their limitations: (a) the unit root test is very sensitive to structural breaks and the results could be misleading (Uctum et al., 2006); (b) it is very difficult to reject a unit root in real debt or in the debt-GDP ratio; and (c) rejection of sustainability based on these two test are invalid because the inter-temporal budget condition (IBC) may well be satisfied, even if the components of the budget are not cointegrated and even if debts or deficits, revenues or spending are difference stationary (Bohn, 2007).
The IBC is
Bohn (1998) proposed a model-based approach to test whether the primary surplus-GDP ratio (st) is a positive and, at least, a linearly rising function of the debt-GDP ratio (dt):
If this property holds, debt is sustainable. That is, if α1 > 0 and statistically significant, debt is sustainable, which means that the initial stock of debt is equal to the sum of the present discounted values of the primary surpluses. The IBC is satisfied if the discounted sum of end-period debt converges to zero. The positive reaction coefficient, α1ensures this convergence.
Bohn (1998) utilises Barro’s (1979) tax-smoothening hypothesis according to which public deficits should be used in order to keep tax rates constant which minimises the excess burden of taxation. Hence, normal expenditure can be financed by regular revenues, and deficits will be incurred to finance unexpected spending. He derives the following fiscal rule or reaction function:
where YVAR and GVAR are business cycle indicators. YVAR accounts for fluctuations in revenues and it gives the deviation of real GDP from its trend, computed using the Hodrick–Prescott (HP) filter. Positive values for YVAR indicate booms and negative values indicate recessions. GVAR gives deviation of real primary spending from its normal value with positive values indicating expenditures above the normal level and vice versa (Greiner & Fincke, 2009).
As the relationship may not be linear and in order to bring this about, the above Bohn model is modified as:
where the reaction coefficient α1 is time-varying. It is, however, noticed that any non-linear model can be approximated by a linear model with time-varying coefficients. The approximation is good if it changes smoothly. So empirical estimation resorts to spline (a type of smoothing technique that allows us to analyse the data in a more flexible way). 9 The functional form or smoothness is shaped by deviations on individual points (i.e., changing points which are termed knots). A p-spline estimation technique is used to estimate the Equation (4). To avoid the endogeneity issue, dt is replaced with dt−1; α1 is the average coefficient and the actual coefficient is the sum of α1 and the deviation, which is given by the smooth function, sm(t). If α1 is positive, there is an indication of debt sustainability, and the time-varying values indicate a change in the response coefficient over the years.
Bohn (1998) is a pioneering study capturing the significance of reaction by analysing the behaviour of the US public debt and deficit (using the Ordinary Least Square Method (OLS) procedure). Abiad and Ostry (2005) extend the basic Bohn framework by adding the extra determinants of a primary balance ratio and panel data of 31 emerging market countries from 1990 to 2002. They have used the panel random effects (RE) procedure, including the spline for debt at a threshold level of 50 per cent of GDP. Haber and Neck (2006) investigate the sustainability of Austrian fiscal policy from a political economy perspective by incorporating certain political variables. Greiner and Kauermann (2008) incorporate the time-varying parameters in the regression (i.e., spline technique) for the European context. Later many studies have used the spline procedure to analyse the debt sustainability issues of various countries (see Fincke & Greiner (2011) for a review of these studies).
In the Indian context, Kaur and Mukharjee (2012) have estimated the fiscal policy response function using the OLS procedure and found evidence of a positive response of the primary surplus ratio to the increasing debt ratio for the combined (centre and states together) data from 1980–81 to 2012–13. By employing the central government’s primary balance and public debt data for the period during 1983–2010 and an OLS procedure, Jose (2014) has generated a similar result. Shastri and Sahrawat (2015) use all three approaches (unit root, cointegration and Bohn) and find that the central government’s revenue and expenditure are not cointegrated. Tiwari (2012) is the only study employing the Bohn framework with spline methodology for national-level (combined) data from 1970 to 2009, but was unable to find clear-cut evidence on sustainability of the public debt.
Summary Results of Important (Selective) Studies on Debt Sustainability
A few studies have dealt with debt sustainability at the sub-national level. For instances, Fincke and Greiner (2011) use the Bohn framework and spline technique to test the debt sustainability of each state in Germany. Employing a panel version (FE model) of the Bohn framework, Mahadavi (2012) analysed the debt sustainability position of 48 US states from 1961 to 2008 and showed that their debt is sustainable. Kaur et al. (2014) used all three empirical models for a panel of 20 major Indian states from 1980–1981 to 2012–2013 and found evidence of sustainability of the aggregate debt position in the long run.
Table 2 provides summary results of a few, selective studies on the topic. It is noticed that none of existing studies in Indian context use the Bohn model to test sustainability at the individual state level. The present study is an attempt to fill this gap.
In order to test the sustainability of public debt in Indian states, this study employs the following extended version of the Bohn framework for panel data:
where sit is the primary surplus-GSDP ratio for the ith state in tth time period; dit–1is the debt-GSDP ratio for the ith state in t − 1 period; and yvarit and gvarit are business cycle variables to account for fluctuations in GSDP and primary public spending, respectively. They are calculated by subtracting the long-term trend of the GSDP (real) from its realised values and the long-term trend of primary spending of the government (real) from its realised values. The long-term trends of the respective variables are computed using the HP filter. λi and µt are the individual (states’) effects and time effects (year), respectively. It is noticed that the lagged debt ratio is used to take into account the endogeneity issue. If ψ > 0 and statistically significant, debt is sustainable.
Descriptive Statistics of the Study Variables (2005–06 to 2014–15)
Results of Panel Unit Root Tests
Panel Model Estimation Results of Bohn Framework for Indian States (Dependent Variable: Primary Surplus to GSDP Ratio)
Penalized Spline Estimation Results of Bohn Model for Indian States
Equation (5) can be estimated using the standard panel data methodologies: fixed effects (FE) and RE. The former posits that the unobserved heterogeneity factors, λi, and time effects, µt, are correlated with other X variables in the equation, while the latter assumes that they are not. The choice of a relevant model depends on the Hausman statistics. If it supports the FEs model, then OLS can be used to estimate equation (5) by incorporating λi and µt with the state and year dummies. If the time dummies are jointly zero, then the model is a one-way FE model. If the Hausman supports the RE model, the GLS estimation procedure can be used.

In order to estimate the time-varying (and state-specific) estimates, this study also uses the p-spline estimation. 10 This allows the reaction coefficient ψ to be a function of time, showing how that coefficients evolve over time and across states. The study uses the following within-estimation specification to employ the p-spline estimation:
where
To check whether debt is sustainable in each sample state, we allow dit−1 to interact with each of the state dummies (Ki) in Equation (6) to get:
The coefficients associated with these interaction terms (ψs) would directly reveal whether debt is sustainable in each state.
To estimate the above equations, the study uses data compiled from various secondary sources for 20 major Indian states: Andhra Pradesh, Assam, Bihar, Chhattisgarh, Gujarat, Haryana, Himachal Pradesh, Jammu Kashmir, Jharkhand, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Odisha, Punjab, Rajasthan, Tamil Nadu, Uttar Pradesh, Uttarakhand and West Bengal. State-wise GSDP (real and nominal) is compiled from the Central Statistical Organization (CSO), Ministry of Statistics and Programme Implementation (MOSPI), Government of India website (
Bohn’s Sustainability Analysis Results
Table 5 presents the estimation results of Equation (5) (Model 1). The Chow test and Hausman statistics support the one-way FE model. The business cycle variable yvar is positive as expected, but not statistically significant even at the 10 per cent level. The primary expenditure gap variable gvar has a negative coefficient and is statistically significant at the 1 per cent level, implying that primary spending above its normal value has reduced the primary surplus ratio. The variable of interest is dit–1. Its coefficnt is positive and statistically significant at the 1 per cent level, indicating the sustainability of public debt in Indian states as a whole. It is noticed that the dependent variable is the primary balance (which may be positive or negative) and when on average the debt-GDP ratio increases by 1 unit, the primary balance-GDP ratio increases by 0.1195 unit. Thus, the latter is a linear and positive function of the former.
Penalized Spline Estimation Results
Column (1) of Table 6 shows the panel within estimation results for comparative purposes. These results are exactly the same as the FE model results shown in Model 1 of Table 5. The p-spline estimation results are shown in Column 2 of Table 6. The estimated parameter of interest associated with the debt ratio, ψ(it) represents the mean of this coefficient, and the smooth term sm(it) shows the deviation from that mean over individual and time-varying coefficients. The results indicate that for Indian states, the reaction coefficient has been positive on average and statistically significant at the 1 per cent level so that the public debt is sustainable. The yvar is not statistically significant even at 10 per cent level; gvar has a negative and significant parameter, implying that public (primary) spending (real) above its normal value has reduced the primary surplus ratio.
The estimated degrees of freedom (edf) of sm(it) provides information on possible time and state dependencies. As the estimated value of edf = 2.58 and the smooth term sm(it) is significant at the 5 per cent level, we may conclude that the reaction coefficient has not stayed constant across states and over time. Figure 2 shows the path of the smooth term; the curve is drawn such that values larger (smaller) than zero indicate that the coefficient was above (below) its average value shown in Column 2 of Table 6. 11
Debt Sustainability Results for Individual States
In order to check whether public debt is sustainable in each state, we estimate Equation (7) by allowing the dit–1 variable to interact with each state dummy. The Chow test and Hausman statistics support the one-way FE model. The estimated results are shown in Table 5 (Model 2). As in Model 1, yvar is not statistically significant and gvar has a negative and significant coefficient. The coefficient of the lagged debt to GSDP ratio and state dummy interaction term ψ is positive and statistically significant for Assam, Bihar, Chhattisgarh, Haryana, Himachal Pradesh, Jharkhand, Kerala, Odisha, Punjab and Uttarakhand, indicating that their public debt is sustainable. For Jammu and Kashmir and Tamil Nadu, the coefficients of debt interaction term are positive but statistically significant only at the 10 per cent level implying that debt is sustainable for these two states too. For Andhra Pradesh, Gujarat, Madhya Pradesh, Rajasthan, Uttar Pradesh and West Bengal, the debt interaction coefficient is positive but not statistically significant even at the 10 per cent level, and for Karnataka and Maharashtra the coefficient is negative but not significant. Therefore, debt is not sustainable in these eight states, so they need corrective actions to make their debt sustainable.
Summary and Conclusion
This study has analysed empirically debt sustainability in 20 major Indian states from 2005–06 to 2014–15, using the extended Bohn sustainability framework for panel data. It has employed three estimation methods: (a) the panel FE model to test whether debt is sustainable in the states as a whole; (b) the panel FE model, including the debt-state dummy interaction term, to test whether debt is sustainable in each state; and (c) the p-spline method to obtain state-specific and time-specific response effects of the debt ratio.
The results indicate that the primary balance of state governments in India reacts (responds) to high public debt as predicted in the Bohn framework. This means that debt policies from 2005–06 to 2014–15 were in general successful in sustaining the debt situation of states as a whole. However, the situation differs by state. Only in 12 out of 20 states, namely, Assam, Bihar, Chhattisgarh, Haryana, Himachal Pradesh, Jammu and Kashmir, Jharkhand, Kerala, Odisha, Punjab, Tamil Nadu and Uttarakhand, is public debt sustainable. The remaining eight states need to take corrective action to tackle their debt situation. One similarity we find in the eight states where debt is unsustainable is that their absolute amount of public debt was relatively high compared to the other states, and ranged between ₹1,600 billion to ₹3,200 billion in 2014–15. We hope these results are useful to policymakers, academicians and other stakeholders in taking appropriate measures to improve the debt situation of states with unsustainable levels of debt.
