be considered the first example of a "stamp tax". When the revenue fell short of expectations in 1608, Venice introduced paper, with the superscription "AQ" and imprinted instructions, which was to be used for "letters to officials". At first, this was to be a temporary tax, but it remained in effect until the fall of the Republic in 1797. Shortly after the introduction of the tax, Spain produced similar paper for general taxation purposes, and the practice spread to other countries. During the 20th century, when many artesian wells were sunk into the periphery of the lagoon to draw water for local industry, Venice began to subside. It was realized that extraction of water from the aquifer was the cause. The sinking has slowed markedly since artesian wells were banned in the 1960s. However, the city is still threatened by more frequent low-level floods—the Acqua alta, that rise to a height of several centimetres over its quays—regularly following certain tides. In many old houses, staircases once used to unload goods are now flooded, rendering the former ground floor uninhabitable. Studies indicate that the city continues sinking at a relatively slow rate of 1–2mm per annum; therefore, the state of alert has not been revoked. In May 2003, Italian Prime Minister Silvio Berlusconi inaugurated the MOSE Project (Modulo Sperimentale Elettromeccanico), an experimental model for evaluating the performance of hollow floatable gates, expected to be completed in late 2023; the idea is to fix a series of 78 hollow pontoons to the sea bed across the three entrances to the lagoon. When tides are predicted to rise above 110 cm, the pontoons will be filled with air, causing them to float on lagoon side while hinged at sea floor on seaside, thus blocking the incoming water from the Adriatic Sea. This engineering work was due to be completed by 2018. A Reuters report stated that the MOSE Project attributed the delay to "corruption scandals". The project is not guaranteed to be successful and the cost has been very high, with as much as approximately €2 billion of the cost lost to corruption. According to a spokesman for the FAI: Mose is a pharaonic project that should have cost €800m [£675m] but will cost at least €7bn [£6bn]. If the barriers are closed at only 90 cm of high water, most of St Mark's will be flooded anyway; but if closed at very