4.1. Data
We combined two sources to obtain firm-level data for the empirical analysis: (1) the Second Economic Census Survey of China on Service Industries in 2008 and (2) the information query platform on the website of Certification and Accreditation Administration of China (CAAC). Though The National Bureau of Statistics of China conducted the Third National Economic Census survey in 2013, firm-level data were not accessible at the time we conducted this research. Thus, the database from 2008 is the most updated one we could access to study the large sample of service firms in China. The dataset of the census provides detailed information of 411,154 service firms, which includes names, addresses, number of employees, four-digit SIC code of each service firm and a series of financial indicators. By searching with firm names and crawling data with a Java-based program, we obtained certificate numbers and other relevant information (such as expiry date, the issuing agencies, and coverage of the certificates) of each service firm that voluntarily participated in the certification (including ISO 9000, ISO 14001 and so on) from the information query platform. In our study, service firms with the certificates labelling “ISO 9000” and “ISO 90001” are both regarded as “ISO 90000 certified”. To eliminate noise from respective certification, former studies generally examined the effects of initial certification on firms [
7]. Similarly, we kept 9253 firms that obtained their initial ISO 9000 certification during 2005–2008 as the treatment group, and 394,624 firms that have no records of certification as our control group.
In this study, we employ the Propensity Score Matching approach to find suitable matches of the certified service firms in the control group. In order to be able to find suitable matches for all exposed subjects, the number of controls available needs to be greater than the number of exposed subjects, and the ratio of such differences is typically in the range of 2–20. To achieve that, we selected firms from 35 major cities across China as 59.6% of Chinse service firms are from these cities, and these 35 major cities are home of 82.2% of the certified service firms. We also deleted firms that have less than eight employees from our dataset because such firms often operated without reliable accounting records. After eliminating firms with missing values and outliers, we obtained a firm-level dataset consisting of 89,024 service firms, and 6071 (6.82%) of them were certified with ISO 9000 standard. Our final dataset can be regarded as a massive survey on ISO 9000 certification. Most firms in the sample are small- and medium enterprises (SMEs). Ninety percent of them hired no more than 70 employees, and nearly 75% of them had total assets valued less than 8 million RMB in 2008.
Table 2 presents the composition of the sample according to their subsectors.
4.2. Analytical Approach
Randomized controlled trials (RCTs) are considered the gold standard approach for estimating the effects of treatments, interventions and exposures on outcomes and random treatment allocation ensures that treatment status will not confounded with either measured or unmeasured baseline characteristics [
39]. If there are selection bias concerning the certification, the results of ordinary regression estimation may also be biased. By constructing a comparison group that shares common characteristics of the certified group, the new sample of service firms can be used to form a near-to-randomized experiment. In this study, we use Propensity Score Matching to conduct a counterfactual experiment and investigate the financial effects of certification. The goal of using it is to approximate a random experiment and estimate the average treatment effect on the treated (ATET), eliminating many of the problems such as selection bias and endogeneity with RCTs in data analysis.
Given a sample of subjects and a treatment, each subject has a pair of potential outcomes: for outcome under control treatment and for outcome of active treatment. Let be the indicator denoting the treatment received. The observed outcome can be expressed as: . For each subject, the average treatment effect (ATE) is defined as , while the average treatment effect on the treated (ATET) is defined as . The ATE is the average effect, at the population level, of moving an entire population from untreated to the treated and The ATET is the average effect of treatment on those subjects who ultimately received the treatment. In estimating the financial effect of ISO 9000 certification, the ATT is more effective for us as we are interested in firms certified with the standard.
The Propensity Score Matching method unitize the probability of treatment assignment conditional on observed baseline covariates to simulate the random assignment of treatment and control groups by matching treated subjects to untreated subjects that were similarly likely in the same group. So it is effective in estimating ATET and underlying the causal effect of treatment variable and it has also been applied to a number of studies with cross-sectional data [
40,
41]. In our case, the propensity scores of each firm is estimated using the logit model:
where
denotes the probability of a firm being certified, and
is a vector of observable characteristics that affect the firm’s certification.
Certification is a dummy variable denoting the certification status, and it equals to 1 if a firm is certified, otherwise the number is zero. The Average Effect of Treatment on the Treated (ATET) of ISO 9000 certification on financial performance can be expressed as:
where
and
represent financial performances of firms in the treatment group and control group respectively. We form matched sets of certified and uncertified firms when they share similar value of propensity score. We use four approaches: the nearest neighbors matching, the radius matching, the kernel matching, and the local linear regression matching to generate the control groups matched. Denote that the matched control group for the certified firm
with characteristics
as the set
, where
is the characteristics neighborhood of
. Let
denote the number of certified firms in the treatment group and let
denote the weight given to
th firm in making a comparison with the
th certified firm,
,where
and
is the set of treated certified firms, and
is an element of the set of matched comparison units. Different matching estimators are generated by varying the choice of
. Then the general formula for the matching ATET estimator is:
Jalan and Ravallion (2003) suggest that the Propensity Score Matching method can allow an assessment of behavioural responses without pre-intervention baseline data and conduct randomization on a condition that both treatment and comparison groups come from the same environment and are given same survey instrument [
42]. Our dataset satisfies this condition. In this study, we have three outcome variables: sales (
lnsale for logarithm of gross sales), productivity (
lp for labor productivity) and profitability (
ros for return on sales). We measure labour productivity with the logarithm of value added per employee. The control group is created based on the estimated propensity score, and the variable vector includes the factors that affect both the treatment and outcome variables [
39,
43]. Existing studies find that including variables that only affect exposure, but not outcome, would increase the variance of the estimated treatment effect [
44,
45]. Following the procedures suggested by Austin (2011), we include variables that affect both the treatment exposure and the performance outcomes to estimate the propensity score [
39]. Another underlying principal is that these variables should not be influenced by the ISO 9000 certification. We also select variables reflecting relatively stable characteristics of the service firms.
The decision for a service firm to be certified is influenced by the characteristics of the firm. As larger firms face a lower cost of certification in terms of the unit of output [
46,
47], we expect that ISO certification be positively related to the size of the firms. The certification with ISO 9000 standard requires substantial financial resources to acquire and maintain the standard of certification [
48]. Therefore, firms’ capabilities to handle finance debt and meet long-term financial obligations are critical for certification. Thus, the likelihood for a firm to be certified is inversely related with the debt–asset ratio of the firm. Moreover, the success of certification is dependent on how employees perceive, accept, and communicate the new practices [
49]. Liu et al. (2010) also reveal that firms’ learning capacity can also affect a firm’s ability to implement the requirements of international certification [
50]. Since human capital is an important factor for learning capacity, we expect that firms with more employees who have college degrees would have a better understanding on ISO 9000 standard and more likely to adopt the certification. As the propensity of being certified is also positively related to the age of firms [
51], we also introduce firm age in our propensity score estimation model. Moreover, firms with high management efficiency tend to apply for the certification [
25]. In this study, management efficiency is measured by management cost divided by total sales, which is negatively related to the management efficiency of the firms.
The external pressures from the operating environment can also affect firms’ decisions to go for certification. We have three variables concerning the operating environment of service firms in China. The first one is the level of industrial competition in the city—which is measured by the Herfindahl–Hirschman index at the 2twodigit SIC industry level in every city. The second variable is the regional market scale of the firms and we measure it with the proportion of manufacturing production in GDP of each city. The third variable is industrial openness, which is estimated by the proportion of foreign ownership in total equity of each four-digit SIC industry. Moreover, we also use dummy variables to capture the two-digit industry fixed effects and provincial fixed effects.
Table 3 reports the descriptive statistics for the variables in the empirical analysis.
Along with the Propensity Score Matching, the Coarsened Exact Matching (CEM) and OLS regression are used as robustness checks. The Coarsened Exact Matching works well without requirements on assumptions about the data generation process. It dominates the existing commonly-used matching methods in its ability to reduce imbalance, model dependence, estimation error, selection bias and some other criteria [
52,
53]. Similar approaches have been applied in previous studies on quality management program and financial performance [
54], ISO 9000 certification and firm process compliance [
35]. In this study, we match each of the certified firms with one non-certified firm for comparison. Then we conduct the OLS regression analysis for the robustness test.