Complex sentence: In 1966, American Express introduced the Gold Card and in 1984 the Platinum Card, clearly defining different market segments within its own business, a practice that has proliferated across a broad array of industries.
Split into simpler sentences: In 1966, American Express introduced the Gold Card. In 1984, the company launched the Platinum Card, clearly defining different market segments within its own business, a practice that has proliferated across a broad array of industries.