PUBLIC International Investments has posted an 84.3 per cent plunge in profit attributable to shareholders to $4.75 million for the year to December 31, from $30.29 million in 1991. ''Net revenue declined primarily due to under-performance of the markets in which the company's overseas subsidiaries operate,'' said company secretary Lai Kim-leong. After-tax profit plummeted 83.7 per cent to $5.03 million, from $30.93 million in 1991. Earnings per share were 1.3 cents, down 84 per cent on the previous 8.3 cents. Directors recommend a final dividend of two cents a share, down 50 per cent on last year's four cents. ''Barring unforeseen circumstances, the board of directors of the company is confident that with the experience and expertise of the management of the new controlling shareholders, the performance of the company will improve significantly during 1993,'' Mr Lai said.