Maritime Transport and Ports

1. Outcome

This Circular provides thematic methodology for compiling ocean accounts relating to maritime transport and port activities. Maritime transport--the movement of passengers and freight by water--is a foundational activity in the ocean economy, carrying more than 80 per cent of global merchandise trade by volume and employing millions of people in vessels, ports, and support services.^[1] At the same time, the sector contributes significantly to air emissions, underwater noise, and other environmental pressures, making integrated accounting essential for sustainable ocean management. The compilation of maritime transport accounts supports three critical decision-use cases: port investment planning (where governments must justify capital expenditure on infrastructure expansion or modernization), shipping decarbonisation tracking (where governments and industry monitor progress toward emissions reduction targets under the International Maritime Organization strategy), and trade facilitation assessment (where analysts evaluate the efficiency and resilience of maritime supply chains).

Upon completion, users will be able to:

• Identify and classify maritime transport and port activities according to ISIC Revision 4 Division 50 (Water Transport) and Class 5222 (Service Activities Incidental to Water Transportation), applying the ocean economy thematic and extended account framework described in TG-3.3 Economic Activity Relevant to the Ocean^[2]
• Compile physical and monetary accounts for shipping emissions, including greenhouse gases and air pollutants, following the SEEA Central Framework air emissions accounting approach detailed in TG-3.4 Flows from Economy to Environment^[3]
• Measure the economic contribution of maritime transport through value added, employment, and trade flows using SNA 2025 production account methods, integrating these measures with the ocean economy structural indicators in TG-2.5 Structure and Function of the Ocean Economy^[4]
• Account for port infrastructure--including land use, dredging, and capital formation--within the asset accounting framework established in TG-3.1 Asset Accounts and extended in TG-6.11 Coastal Infrastructure Accounting^[5]
• Record environmental interactions including ballast water, hull biofouling, anchoring impacts, and underwater noise as residual flows and ecosystem condition impacts, linking to the emissions methodology in TG-2.8 Climate Indicators^[6]

This Circular connects maritime transport accounts upward to broader ocean economy measurement (TG-2.5 for transport GVA shares and employment), climate policy (TG-2.8 for shipping emissions tracking), infrastructure investment (TG-6.11 for port capital stock), and labour accounts (TG-3.4 Labour Accounts for seafarer and port employment). These linkages enable maritime transport data to populate the indicator frameworks for SDG 14 (Life Below Water) target 14.7 on sustainable use of marine resources and SDG 13 (Climate Action) through emissions monitoring.

2. Requirements

This Circular builds upon the following prerequisites:

• TG-0.1 General Introduction to Ocean Accounts -- provides the foundational framework for GOAP Technical Guidance, including core concepts, terminology, and the relationship between environmental-economic accounting and ocean governance. Users should be familiar with the accounting principles and classification structures described therein before proceeding.

• TG-3.3 Economic Activity Relevant to the Ocean -- establishes the general approach to compiling accounts for ocean-related economic activity, including industry classifications, supply and use tables, and the ocean economy thematic and extended account framework. The maritime transport accounts compiled under this Circular are a sector-specific application of the methods described in TG-3.3.

Users should complete these prerequisites before implementing this Circular to ensure a proper understanding of the underlying accounting frameworks and classification systems.

Related Circulars (optional but recommended):

• TG-2.5 Structure and Function of the Ocean Economy -- for the indicator derivation methodology that transforms maritime transport accounts into policy-ready metrics, including transport GVA shares, employment intensity, and contribution to exports.

• TG-2.8 Climate Indicators -- for GHG emission indicators and their integration into climate change monitoring frameworks, particularly shipping's contribution to national emissions inventories.

• TG-3.1 Asset Accounts -- for the produced asset accounting framework underlying the valuation of port infrastructure and vessel capital stock.

• TG-3.4 Flows from Economy to Environment -- for detailed emissions accounting methodology, including the classification of residual flows from economic activities to the environment that underpins the shipping emissions accounts in Section 3.3.

• TG-4.1 Remote Sensing -- for port area spatial delineation using satellite imagery and geographic information systems, which supports the land use mapping described in Section 3.2.1.

• TG-6.9 Offshore Energy -- for accounting treatment of offshore support vessels and the maritime logistics of offshore energy installations.

• TG-6.11 Coastal Infrastructure Accounting -- for the broader infrastructure accounting framework within which port capital formation is situated.

3. Guidance Material

3.1 Maritime Transport Activities

3.1.1 Industry Classification Framework

Maritime transport activities are classified according to the International Standard Industrial Classification of All Economic Activities (ISIC) Revision 4.^[7] The primary classification is:

Division 50 -- Water Transport

This division encompasses the transport of passengers or freight over water, whether scheduled or not. ISIC Rev.4 specifies: "This division includes the transport of passengers or freight over water, whether scheduled or not. Also included are the operation of towing or pushing boats, excursion, cruise or sightseeing boats, ferries, water taxis etc."^[8] The division distinguishes between sea-going vessels and inland waterway vessels based on the type of vessel used, not solely on geographic location.

The division distinguishes between two main groups:

These codes have been verified against the official ISIC Rev.4 publication.^[9] Compilers should also note the correspondence with the Central Product Classification (CPC) Ver.2.1 for product-level analysis of transport services, which aligns with the supply and use table approach described in TG-3.3 Economic Activity Relevant to the Ocean.

Supporting Activities (Division 52)

ISIC Rev.4 defines Class 5222 as covering "activities related to water transport of passengers, animals or freight: operation of terminal facilities such as harbours and piers, operation of waterway locks etc., navigation, pilotage and berthing activities, lighterage, salvage activities, lighthouse activities."^[10]

Related Manufacturing (Division 30)

3.1.2 Vessel Categories

For accounting purposes, the commercial fleet may be disaggregated by vessel type:^[11]

1. Container vessels -- carry standardised cargo containers
2. Bulk carriers -- dry bulk cargo (grains, ores, coal)
3. Tankers -- liquid bulk cargo (oil, chemicals, liquefied gas)
4. General cargo vessels -- non-containerised cargo
5. Roll-on/roll-off (Ro-Ro) vessels -- wheeled cargo
6. Passenger vessels -- ferries and cruise ships
7. Fishing vessels -- commercial fishing (cross-reference TG-6.7 Fisheries Stock Assessment)
8. Service vessels -- tugs, dredgers, offshore support vessels (cross-reference TG-6.9 Offshore Energy for vessels supporting offshore installations)

This disaggregation is important for emissions accounting because emission factors vary significantly by vessel type, size, and engine configuration. The vessel classification should be used consistently across physical activity accounts, economic accounts, and emissions accounts to enable meaningful cross-tabulation. The Fourth IMO GHG Study (2020) provides comprehensive emission factor data by vessel type and operating mode that can serve as a starting point where country-specific factors are not available.^[12]

3.1.3 Trade Flow Measurement

Maritime trade flows are measured through:

• Volume (physical): Tonnes loaded and unloaded at ports
• Value (monetary): Value of goods transported (CIF/FOB basis)^[13]
• Activity (operational): Vessel movements, port calls, cargo handling operations

Data sources include port authority records, customs declarations, automatic identification system (AIS) tracking, and shipping company reports. AIS data in particular has become a valuable source for activity-based measurement, providing near-continuous records of vessel positions, speeds, and headings that can be linked to emission estimation models and trade flow analysis. The global AIS network now provides coverage for approximately 95 per cent of commercial vessels over 300 gross tonnes, enabling detailed spatial analysis of shipping activity patterns.^[14]

3.2 Port Infrastructure

3.2.1 Port Areas and Land Use

Port infrastructure accounting requires spatial delineation of port areas. Port lands typically include:^[15]

• Quays and berths -- vessel mooring facilities
• Storage areas -- container yards, warehouses, tank farms
• Intermodal connections -- rail terminals, road connections
• Administrative areas -- offices, customs facilities
• Ancillary facilities -- ship repair, bunkering stations

Port areas should be mapped using consistent spatial references (see TG-4.1 Remote Sensing) and linked to the SEEA land cover and land use classifications.^[16] When constructing spatial accounts, the port boundary should encompass the full operational area including anchorages, fairways, and approach channels, as these areas are subject to environmental management and may overlap with marine spatial planning zones.

3.2.2 Dredging and Land Reclamation

Dredging activities modify the seabed to maintain or create navigational channels and berthing areas. Accounting for dredging includes:^[17]

Physical measures:

• Volume of sediment removed (cubic metres)
• Disposal location (ocean dumping, beneficial reuse, confined disposal)
• Channel depth and width specifications

Economic measures:

• Dredging expenditure by capital vs. maintenance
• Cost allocation to port operations

Environmental considerations:

• Sediment quality (contaminant levels)
• Impacts on benthic habitats
• Turbidity and sedimentation effects

Land reclamation for port expansion should be recorded as a transformation of marine extent to land (cross-reference TG-3.1 Assets).^[18] This transformation represents a change in ecosystem extent that should also be reflected in ecosystem extent accounts where compiled. Port expansion through reclamation may also trigger requirements under coastal infrastructure accounting (see TG-6.11 Coastal Infrastructure Accounting), particularly where protective structures such as breakwaters and seawalls are constructed as part of the development.

3.2.3 Port Capital Formation

Gross fixed capital formation in ports includes investment in:^[19]

• Breakwaters and seawalls
• Quay structures and berths
• Container handling equipment (cranes, straddle carriers)
• Warehouses and storage facilities
• Navigational aids and vessel traffic systems
• Environmental protection infrastructure (oil spill response, waste reception)

Capital formation should be recorded following SNA 2025 principles, distinguishing between new construction and major improvements (gross fixed capital formation) and routine maintenance (intermediate consumption). Depreciation schedules for port infrastructure vary considerably by asset type--quay structures may have useful lives of 50 years or more, while handling equipment typically depreciates over 15--25 years. The perpetual inventory method (PIM) provides the standard approach for compiling port capital stock, applying asset-specific depreciation rates to historical investment series.^[20]

3.3 Emissions Accounting

3.3.1 Greenhouse Gas Emissions

Maritime transport is a significant source of greenhouse gas (GHG) emissions. According to the SEEA Central Framework, air emissions accounts record the generation of emissions by resident economic units by type of substance.^[21]

GHG emissions from shipping include:

Estimation methodology:

Shipping emissions are typically estimated using activity-based methods:^[22]

$$E = \sum_{v} \sum_{m} (A_{v,m} \times EF_{v,m})$$

Where:

• E = Total emissions
• A = Activity (fuel consumption or distance travelled)
• EF = Emission factor
• v = Vessel type
• m = Operating mode (cruising, manoeuvring, at berth)

Data sources:

• Ship fuel consumption records
• AIS-derived activity data
• Port call statistics
• National fuel sales data with maritime allocation

The Fourth IMO GHG Study (2020) provides comprehensive emission factor data by vessel type and operating mode. Compilers may also draw on the IPCC 2006 Guidelines, Volume 2, Chapter 3 for default emission factors for mobile combustion sources.^[23]

Table 3.3.1: Shipping emission calculation methods

Residence principle application:

Following the SEEA CF residence principle, emissions should be attributed to the country where the operating enterprise is resident, not the flag state of the vessel.^[24] This alignment with national accounts principles is essential for consistent ocean economy thematic and extended accounts. In practice, this means that emissions from a vessel flagged in one country but operated by an enterprise resident in another country should be attributed to the country of the operator. Where vessel ownership is dispersed across multiple jurisdictions through complex corporate structures, compilers should follow the ultimate beneficial ownership principle consistent with SNA 2025 guidance on globalisation and institutional units.

3.3.2 Air Pollutants

Beyond GHGs, maritime transport releases air pollutants with local and regional health impacts:^[25]

The International Maritime Organization (IMO) regulates these emissions through MARPOL Annex VI and has established Emission Control Areas where stricter limits apply. The 2020 global sulphur cap of 0.50 per cent m/m, reduced from the previous 3.50 per cent, has had a material effect on fuel composition and emissions profiles that should be reflected in time series accounts.^[26]

For linkage to health impacts, see TG-2.7 Pollution and Other Flows. For integration of shipping GHG emissions into national climate indicator frameworks, see TG-2.8 Climate Indicators.

3.3.3 Underwater Noise

Shipping is a major source of chronic underwater noise pollution, particularly at low frequencies (10--1000 Hz) that overlap with marine mammal communication bands.^[27]

Noise emissions can be characterised by:

• Source level (dB re 1 microPa at 1 m)
• Frequency spectrum
• Temporal patterns (continuous vs. intermittent)

Accounting for underwater noise requires:

• Vessel traffic density data (AIS)
• Source level models by vessel type and speed
• Propagation modelling for spatial distribution
• Overlay with sensitive habitats and species distributions

Underwater noise accounting is an emerging area where data availability and standardised methods remain under development. The IMO Guidelines for the Reduction of Underwater Noise from Commercial Shipping (MEPC.1/Circ.833) provide a framework for voluntary measures, while regional initiatives such as the Joint Monitoring Programme for Ambient Noise in the North Sea (JOMOPANS) are developing monitoring methodologies.^[28] Compilers should record noise indicators where feasible and note limitations in metadata. For linkage to ecosystem condition assessment, see TG-2.1 Biophysical Indicators, which provides guidance on integrating pressure indicators such as underwater noise into condition accounts.

3.4 Economic Measurement

3.4.1 Value Added

Maritime transport value added is calculated according to SNA 2025 principles:^[29]

Gross Value Added (GVA) = Output -- Intermediate Consumption

For maritime transport industries (ISIC 50, 5222):

• Output = Freight revenue + passenger revenue + charter income + ancillary services
• Intermediate consumption = Fuel, port fees, insurance, maintenance, provisions

Net Value Added = GVA -- Depreciation

Illustrative calculation structure:

This table structure should be populated using national data sources such as structural business surveys, port authority financial statements, and maritime industry associations. For countries with significant transshipment activities, care should be taken to correctly attribute output to the resident enterprises performing the transport service, consistent with the balance of payments treatment of freight transport described in BPM6.

3.4.2 Employment

Employment in maritime transport includes:^[30]

Seafarers:

• Officers and ratings on commercial vessels
• Measured by nationality (flag state vs. residence state considerations)

Shore-based employment:

• Port workers (stevedores, crane operators)
• Port authority and maritime agency staff
• Ship agents, freight forwarders
• Ship repair and maintenance workers

Employment data should distinguish:

• Number of persons employed
• Full-time equivalents (FTEs)
• Hours worked
• Compensation of employees

3.4.3 Supply Chain Linkages

Maritime transport has extensive backward and forward linkages:^[31]

Backward linkages (inputs):

• Shipbuilding and repair (ISIC 3011)
• Fuel suppliers
• Port services
• Classification societies
• Marine insurance

Forward linkages (outputs):

• Wholesale and retail trade
• Manufacturing (imported inputs)
• Agriculture (commodity exports)
• Tourism (cruise industry)

These linkages can be quantified using supply and use tables and input-output analysis (see TG-3.3 Economic Activity Relevant to the Ocean).^[32] The maritime transport multiplier effect--capturing indirect and induced economic activity--can be estimated from input-output tables where these are available at sufficient industry detail. This is particularly relevant for small island developing States where maritime transport may constitute a substantial share of GDP.

3.5 Environmental Interactions

The environmental interactions of maritime transport span multiple flow types within the SEEA framework. Table 3.5.1 summarises the main interactions and their corresponding SEEA account entries, with cross-references to the relevant guidance circulars.

Table 3.5.1: Maritime transport environmental interactions and SEEA flow types

3.5.1 Ballast Water

Ships take on ballast water for stability, potentially transporting organisms across biogeographic boundaries. Ballast water exchanges introduce invasive species that can devastate local ecosystems.^[33]

Accounting elements:

• Volume of ballast water discharged (by port, by vessel origin)
• Species detection monitoring
• Compliance with Ballast Water Management Convention
• Expenditure on ballast water treatment systems

Cross-reference: Invasive species impacts should be linked to ecosystem condition accounts (see TG-2.1 Biophysical Indicators).

3.5.2 Hull Biofouling

Organisms attach to vessel hulls and can be transported to new locations, similar to ballast water. Hull biofouling is a pathway for invasive species introduction.^[34]

Accounting elements:

• Antifouling system application and maintenance
• Hull cleaning activities and waste disposal
• Biofouling inspections at ports
• Linkage to invasive species monitoring

The recording of biofouling management expenditure serves as both an environmental protection expenditure and an input to estimating the risk of species transfer across maritime routes.

3.5.3 Anchoring Impacts

Anchoring causes physical damage to seabed habitats, particularly seagrass meadows and coral reefs.^[35]

Accounting elements:

• Anchorage locations and frequency of use
• Duration of anchor events
• Overlap with sensitive habitat areas
• Mooring buoy installation as mitigation

Cross-reference: For seagrass and coral reef extent and condition, see TG-6.1 Coral Reef and TG-6.3 Seagrass.

3.5.4 Oil and Chemical Spills

Despite improved safety, shipping remains a source of marine pollution from accidental and operational discharges.^[36]

Accounting elements:

• Spill volume and substance type
• Location and environmental sensitivity
• Response costs
• Natural resource damage assessments
• Linkage to SEEA pollution flow accounts (TG-3.4 Flows from Economy to Environment)

The long-term trend in large oil spills from tankers has been declining, but operational discharges (bilge water, cargo residues) remain a persistent source of chronic pollution that should be captured in flow accounts alongside acute events.

3.6 Compilation Procedure: Maritime Transport Supply-Use Table

Compiling maritime transport accounts follows a systematic procedure for extracting maritime transport sub-matrices from national supply and use tables and deriving indicators from them. This procedure is adapted from the SNA 2025 treatment of supply and use tables (Chapter 15) and the ocean economy thematic account compilation approach in TG-3.3 Economic Activity Relevant to the Ocean Section 3.4.^[37]

Step-by-step compilation

Step 1: Identify maritime transport industries by ISIC code. Using Table 3.1.1 in Section 3.1, identify all ISIC classes that constitute maritime transport in the compiling country: Division 50 (Water Transport), Class 5222 (Service Activities Incidental to Water Transportation), Class 5224 (Cargo Handling, port portion), and related industries. For each class, determine whether it is wholly maritime-related (ocean ratio = 1.0) or partially maritime-related (ocean ratio < 1.0).

Step 2: Extract maritime transport sub-matrices from national SUTs. From the balanced national supply and use tables, extract the columns corresponding to identified maritime transport industries. This creates a maritime transport supply table and a maritime transport use table that are subsets of the national tables.

Step 3: Determine the maritime share for mixed industries. For partially maritime-related industries (e.g., cargo handling where both port and airport operations occur), estimate the share of output directly attributable to maritime activity. For Class 5224 (Cargo Handling), if 70 per cent of cargo handling output in a country serves maritime transport demand, the maritime ratio for that industry is 0.70.

Step 4: Calculate Maritime Transport Direct GVA. For each maritime industry, multiply the industry's gross value added from the Use Table by its maritime ratio:

$$\text{Maritime Transport Direct GVA} = \sum_i (\text{GVA}_i \times \text{Maritime ratio}_i)$$

Step 5: Compile employment accounts. Using labour input rows from the Use Table, calculate maritime transport employment by applying the same maritime ratios to employment data by industry.

Step 6: Derive trade flow indicators. From the Exports column in the Use Table, sum across maritime transport service products (freight services, passenger services) to calculate maritime transport service exports. From customs data, compile merchandise trade volumes and values passing through ports.

Step 7: Integrate emissions accounts. Using the emissions calculation methods in Section 3.3, compile air emissions by maritime transport industries from national air emissions accounts, ensuring consistency with the GVA and activity data in the maritime transport SUTs.

Data sources

Key data sources for maritime transport account compilation:^[38]

• National supply and use tables (primary source for GVA and output)
• Port authority statistical reports (cargo volumes, vessel calls, employment)
• Maritime administration records (vessel registries, seafarer certification)
• Structural business surveys (port and shipping company financial data)
• Customs declarations (trade values and volumes)
• AIS tracking data (vessel activity, voyage data)
• Fuel sales records (maritime fuel consumption for emissions)

3.7 Worked Example: Synthetic Port/Shipping Account

This section presents a worked example demonstrating the compilation of a maritime transport account for a synthetic medium-income coastal state ("Country B"). Country B has a total GDP of approximately USD 80 billion, total employment of 15 million persons, and two major ports handling combined cargo volumes of 45 million tonnes per year.

Table 3.7.1: Country B Maritime Transport Account -- Production Account

All monetary values in millions of USD at current prices.

Table 3.7.2: Country B Maritime Transport Employment

The labour productivity calculation shows that sea transport (ISIC 501) exhibits higher productivity than port services (ISIC 5222), reflecting the capital-intensive nature of vessel operations relative to port labour.

Table 3.7.3: Country B Maritime Transport Emissions

The emission intensity indicator reveals that sea transport generates approximately 1.9 tonnes of CO2e per thousand dollars of GVA, substantially higher than port services, due to fuel combustion in vessel operations.

Table 3.7.4: Country B Port Infrastructure Capital Stock (PIM approach)

All monetary values in millions of USD at current replacement cost. The net capital stock of USD 1,270 million represents approximately 4.2 times the annual GVA from port services (USD 300 million), indicating a capital-intensive industry with long-lived infrastructure assets.

Interpretation: This worked example demonstrates how maritime transport accounts integrate production accounts, employment accounts, emissions accounts, and asset accounts into a coherent framework. The maritime transport sector contributes 1.2 per cent of Country B's GDP (USD 950 million / USD 80 billion) while employing 0.27 per cent of the workforce (40,000 / 15 million), indicating above-average labour productivity. The emission intensity of 1,418 kg CO2e per USD 1,000 of GVA is consistent with the fuel-intensive nature of maritime transport and provides a baseline for tracking decarbonisation progress under IMO targets.

4. Acknowledgements

This Circular has been approved for public circulation and comment by the GOAP Technical Experts Group in accordance with the Circular Publication Procedure.

Authors: GOAP Secretariat

Reviewers: To be assigned

Contributing frameworks and sources:

This Circular draws upon:

• SEEA Central Framework (UN et al., 2012)
• ISIC Revision 4 (UN, 2008)
• SNA 2025 (UN et al., 2025)
• MARPOL Convention (IMO)
• Ballast Water Management Convention (IMO)
• Fourth IMO GHG Study (IMO, 2020)
• UNCTAD Review of Maritime Transport
• IPCC Guidelines for National Greenhouse Gas Inventories

5. References