affected one month after a flood than in the immediate aftermath. This suggests that damages are passed on through transmission channels over time. Indeed, the main reasons why firms experienced a fall in sales relate to supply chain issues—either as transportation routes are disrupted, or as clients experience financial losses, which are partly passed on from their own clients. Overall, about 75 percent of affected firms reported reduced sales a month after a disaster.

The survey also reveals that natural shocks affect the ability of employees to commute and work (and thus earn an income), and hence obstruct firms’ ability to continue operations. Disruptions to public transport are highly significant for commuters in all three study areas. In an average firm, about 69 percent of workers use the bus as their main mode of transport to work. This is followed by walking (20 percent), motorbike (5 percent), and bike (2.6 percent). About 41 percent of firms reported that damaged public transport infrastructure prevented workers from coming to work in the aftermath of floods, including lowintensity flooding during regular rainy seasons.

During floods and heavy rainfall, water and power outages are common in Tanzania; 81 percent of surveyed firms experienced a power outage during the most serious disaster, lasting on average 4.9 days. More firms in Dar es Salaam (91 percent) and Tanga (84 percent) experienced power outages than in Dodoma (28 percent). However, the outages lasted longer in Dodoma and Tanga (12 days) than Dar es Salaam (2.7 days). Three-quarters of firms do not have an alternative electricity source, but 23 percent reported switching to a generator when facing a power outage. Mean costs of the back-up electricity supply are comparable to normal electricity costs.

While Tanzanian firms already face frequent electricity and water disruptions during the dry season, the survey shows that these are amplified in the rainy season. An average firm experiences power outages on about 2.6 days per month in the dry season, with this number nearly doubling to 5.1 days in the rainy season, when outages also last longer. While the mean outage duration is about 5.4 hours in the dry season, these increase to around 11.2 hours in the rainy season. Taking both effects into account and correcting for outliers, an average firm experiences around 17.8 total hours of power outage each month in the dry season, rising to 57 hours in the rainy season.

The lack of reliable and resilient infrastructure systems causes economic efficiency losses. A global study by Rentschler et al (2019) highlights the substantial drag that unreliable infrastructure imposes on firms in developing countries. In Tanzania, firms are incurring estimated utilization losses of nearly $670 million a year (1.8 percent of national GDP) from power and water outages and transport disruptions. The firm survey collected for this study allows us to estimate the share of these utilization losses that are caused by natural shocks. Power disruptions alone are responsible for $216 million in utilization losses a year, of which 47 percent ($101 million, or 0.3 percent of GDP) are solely due to power outages caused by rain and floods. The remaining 53 percent are due to baseline power outages associated with causes other than rain and flooding (such as load shedding or equipment failure). For transport disruptions, about 46 percent of utilization losses ($150 million, or 0.4 percent of GDP) are due to disruption caused by rain and floods. The survey does not find that rain and floods have any significant impact on the incidence of water supply disruptions.

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