a reduction in the conversion rate applicable on 1 January 1999 which is greater in absolute value than the differences between that rate and the lowest levels of the conversion rates applicable: - over the last 12 months, and - at any time more than 12 months but not more than 24 months previously, and - at any time more than 24 months but not more than 36 months previously, a situation where the annual average exchange rate is below a threshold defined as the lowest average annual conversion rate applied during the preceding three years and the exchange rate of 1 January 1999