"The national accounts suffer from insufficient data sources and undeveloped statistical techniques," an IMF country report following so-called Article IV consultations on Sri Lanka said.
"The country does not have periodic comprehensive benchmarks or a system of regular annual surveys of establishments. A statistical business register, which would serve as the main basis for conducting sample surveys, is not available.
"As a result, the few surveys that are conducted do not have good sample frames.
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But most the underlying data are timely, the report said.
"However, detailed data needed to measured both output and intermediate consumption are mostly unavailable or not collected," the report cautioned.
"As a result, the estimates of gross value added are prepared directly relying on outdated fixed ratios established from the base year 1996, often with outdated studies or ad hoc assumptions.
"Quarterly indicators are used for compiling quarterly value-added estimates.