/**
 * Estimate the world population at a moment in time. Defaults to now.
 */
export declare function estimate(date?: Date): number;
/**
 * The average number of milliseconds between each birth at a moment in time.
 * Defaults to now. Useful for incrementing counters.
 */
export declare function interval(date?: Date): number;
/**
 * Estimate the date that the population will reach a certain value (for the
 * first time)
 * @param population
 */
export declare function estimateDate(population: number): Date;