A trainer picks up Chinese Yuan banknotes from the open mouth of a crocodile during a performance at a zoo in Wenling, Zhejiang province March 2, 2015. REUTERS/Stringer China just delivered its lowest GDP growth figure in 25 years.

On Monday, China lowered its GDP growth figure to 7.3%, from its January number of 7.4%.

Not only is its the slowdown freaking out investors, the revision once again throws the accuracy of China's data reporting into the limelight.

It's well-documented that China's economic data releases are a conundrum for investors. Many don't fully believe the government is telling the truth.

However, speaking to the BBC this morning, Jeremy Penn, chief executive of maritime market data organisation Baltic Exchange, said one of the ways to determine the health of the Chinese economy is through shipping. "The position of shipping of raw materials into China is a clear indicator," said Jeremy Penn, chief executive of maritime market data organisation Baltic Exchange to the BBC.

"In the early part of this year, March or April, we saw for the first time in many years a decline in absolute numbers for steel production in China, and that's reflected through now into the import levels for coal and iron ore, and the shipping rates, which are associated with those types of ships."

In other words, you can compare raw shipping figures from places like Baltic Exchange with that of the Chinese government, and deduce what it says about imports and exports.

Penn added that China's shipping growth slowed down for the first time in 12 years without giving specific figures.

The Baltic Dry Index, a measure of shipping that is heavily dependent on the strength of China imports, is at a 1 month low, according to Bloomberg:

It has also hit record lows this year, per City AM:

The Baltic Dry Index, which tracks the movement of raw materials, fell to its lowest level since 1985 earlier this year, while the index was 43 per cent weaker than the previous year.

Part of this is down to China, which has turned away from coal towards cleaner energy sources. And a more general slowdown in the country’s economy has led to a reduction in imports of materials like iron.