We use a structural discrete choice labour supply model to estimate labour supply elasticities and to assess the labour supply effects of the Austrian tax reform of 2016. To do so we implement the new rules and regulations of the tax reform in the IHS Labour Supply Model for Austria ILSA.Footnote 5
ILSA is a structural discrete choice labour supply model that allows for the estimation of static uncompensated own and cross-wage elasticities at the intensive and extensive margin. The advantage of discrete choice models is that they directly account for the fact that observed hours of work cluster around zero and full-time hours and incorporate both the intensive and extensive margin of labour supply (Bargain et al. 2014). Furthermore, as it is not necessary to specify the entire budget constraint, the discrete choice approach is well suited to the complexities of the tax benefit system and its interplay with means tested benefits given the labour supply of different members of one household. For each hours choice transfer entitlements and take home pay are directly evaluated.Footnote 6
As many micro-simulation models ILSA views labour supply decisions of individuals and couples as an optimal choice from a discrete set of working hours categories (VanSoest 1995; Creedy and Kalb 2005). The observed working hours are interpreted as the result of utility maximisation of households, and therefore represent the trade-off between consumption (income) and leisure. For couple households, the existence of a joint utility function is assumed, that features household income and both partners’ leisure as an argument. This approach allows for the estimation of the structural parameters of the underlying utility function through a multinomial logit model. Based on these estimates the behavioural response to a given change in disposable income can be quantified, such that second round distributional effects can be evaluated on individual as well as aggregate level.
To be more specific, we follow VanSoest (1995) and interpret labour supply as a choice of unitary households n = 1, ..., N from a discrete set of alternatives j = 1,..., J.
Every discrete alternative is a combination of the disposable income of the household \(y_{nj}\) and the male \(m_{nj}\) and female \(f_{nj}\) leisure time. Leisure time is the total time endowment (168 h) minus corresponding hours worked. The gross hourly wage rates are \(w_{n}^{m}\) and \(w_{n}^{f}\). Thus, the disposable income is a function of the male \(h_{nj}^{m}\) and female \(h_{nj}^{f}\) working time and the wage rates minus taxes \(\tau\):
$$\begin{aligned} y_{nj} = w_{n}^{m}h_{nj}^{m} + w_{n}^{f}h_{nj}^{f} - \tau (w_n^{m}h_{nj}^{m},w_{n}^{f}h_{nj}^{f};Z_{n}). \end{aligned}$$
(1)
The tax-benefit function expresses the individual tax burden. This depends on the male and female gross income as well as on household characteristics \(Z_{n}\), e.g. whether a child is living in the household. Non-labour income (e.g. transfers) is included in the disposable income, also influenced by the household characteristics. For the working hours we divide the continuum of possible working hours in six categories and define the median working hours in a group as the discrete alternative. The distribution of working hours within each group differs for males and females, thus we have slightly different discrete alternatives for males and females. The discrete alternatives are given by the medians of the following working hours groups: 0, 1–10, 11–20, 21–30, 31–40, 40+.
The six individual choice alternatives lead to 36 choice alternatives in the household decision model. The gross hourly wages are calculated from our annual data using working hours per week, number of months in employment and the gross yearly income. Wages in the upper and lower 1% percentile are truncated. For these observations and when wages are not observable (e.g. if non-employed) a Heckman model is estimated to correct for sample selection (Heckman 1976, 1979).Footnote 7
The utility of the household is given by a systematic part \(V_{nj} = V(y_{nj},m_{nj},f_{nj};Z_{n})\) and a random error following an extreme value distribution of type I: \(U_{nj} = V_{nj} + \varepsilon _{nj}, \forall n,j\). For the systematic part we further assume a quadratic form and potential interactions:
$$\begin{aligned} V_{nj} & = \overline{\alpha }_{y}y_{nj} + \overline{\alpha }_{m}m_{nj} + \overline{\alpha }_{f}f_{nj} + \beta _{y2}y_{nj}^{2} + \beta _{m2}m_{nj}^{2} + \beta _{f2}f_{nj}^{2}\nonumber \\& \quad + \beta _{ym}y_{nj}m_{nj} + \beta _{yf}y_{nj}f_{nj} + \beta _{mf}m_{nj}f_{nj}. \end{aligned}$$
(2)
We account for observed heterogeneity among the households through the vectors \(\overline{\alpha }_{y}, \overline{\alpha }_{m}\) and \(\overline{\alpha }_{f}\). Each of these vectors contains the direct preference and measures the effect of each household characteristic through taste-shifting parameters \(\overline{\gamma }_{y}, \overline{\gamma }_{m}\) and \(\overline{\gamma }_{f}\):
$$\begin{aligned} \overline{\alpha }_{y}&= \beta _{y} + Z_{n}^{'}\overline{\gamma }_{y}\end{aligned}$$
(3)
$$\begin{aligned} \overline{\alpha }_{m}&= \beta _{m} + Z_{n}^{'}\overline{\gamma }_{m}\end{aligned}$$
(4)
$$\begin{aligned} \overline{\alpha }_{f}&= \beta _{f} + Z_{n}^{'}\overline{\gamma }_{f}. \end{aligned}$$
(5)
As taste-shifting parameters we include age, work experience, education, other household income (e.g. from other members of the household inflexible in their labour supply), number and age of children and whether a person lives in Vienna. The impact of further direct preferences are measured via parameter \(\beta _{y}\), \(\beta _{m}\) and \(\beta _{f}\).
For single males and females the disposable income (1) in the utility function (2) depends only on the net income of the individual plus possible transfers (depending on household characteristics, such as children). Similar taste shifters apply as in the household model, but here we also consider whether the person lives alone.
Using the unitary household model and the individual models for males and females we calculate labour supply elasticities for married and single males and females in Austria. Building on our results we estimate the labour supply effect of the Austrian tax reform of 2016. We present changes at the intensive and extensive margin for ten different income levels.