# 3. Data and methodology

## 3.1. A dedicated firm survey

This study presents evidence from a dedicated Tanzanian firm survey conducted with 837 businesses in Dar es Salaam and the provinces of Tanga and Dodoma. The survey explores the real costs of disasters on firms—both through direct damage to assets and operations, and the indirect costs of perpetuated economic inefficiencies and coping measures. The survey’s target population was all 58,959 firms in Dar es Salaam, Tanga, and Dodoma that were registered with the National Bureau of Statistics’ (NBS) in 2015. This excluded informal firms, which contribute significantly to the Tanzanian economy (Adams et al. 2013). Firms listed in the NBS registry without a contact telephone number were also excluded from the sampling frame. Hence, all survey results should be interpreted as representative of more formal business activities.

To ensure that robust estimation results can be obtained for different subpopulations, the survey used a dedicated sampling strategy. Based on information from the NBS, all registered firms were divided into five distinct strata, depending on their reliance on transport systems. Ordered from low to high transport reliance, these strata contain firms from the following sectors:

1. Accommodation and food service activities, Construction

2. Communication and other services 3. Manufacturing, Mining, Water, Energy, Agriculture 4. Transportation and storage 5. Wholesale and retail trade, Repair of motor vehicles and motorcycles The sample selection was completed in one stage, with firms selected through a systematic random sampling method from each stratum. In terms of regional distribution, the sample contains 623 firms from Dar es Salaam, 101 from Dodoma, and 113 from Tanga. For a full overview of the total and sampled number of firms by region and strata, see Table A.1 (appendix A). The survey was implemented over 50 days between Tuesday 25<sup>th</sup> September and 13<sup>th</sup> November 2018. About 10 percent of listed firms were interviewed, with the main reasons for the low response rate being incorrect addresses, expectation of payment for survey participation, and concerns about disclosure of tax-relevant information.

The survey contained about 390 questions divided into nine modules focusing on various aspects, including reliance on different infrastructure types, disaster experience, information on suppliers and clients, and firm characteristics such as size, investment volumes, and operational costs. All results in this study are based on data collected through this survey, unless otherwise stated. Tables 1–4 present an overview of the average characteristics, infrastructures and dependencies, expenditures and investments of firms in Dar es Salaam, Dodoma and Tanga computed from the survey.

**Table 1: Descriptive statistics on firms' characteristics**

|**Variable**|**Available**<br>**observations**|**Mean**|**Median**|**Standard**<br>**deviation**|**Min**|**Max**|
|---|---|---|---|---|---|---|
|Age of firm (years)|837|12.44|9|12.08|1|85|
|Number of employees, including owner|837|14.73|4|179.77|1|8,501|
|Share of female workers|757|36.6%|30%|36.0%|0%|100%|
|Number of suppliers|805|8.11|7|8.91|1|165|
|Share of firms selling to general public|837|89.3%|1|1.09%|||

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