After visiting the current exhibition of corporate art at Shibuya's Bunkamura, I have arrived at a daring new explanation of Japan's economic downturn. But more on this later.

During the bubble years, while Japanese companies were working flat out to take over the world economy, they were also greedily buying up much of the world's best art.

Since 1994, in a brave attempt to ensure that these works are not lost to the public eye, Bunkamura has been gathering the best art from company boardrooms and obscure corporate museums to show in a high-profile collection every few years.