The surge in corporate profit margins is exclusively a large-cap phenomenon, highlighting a stark divide on Wall Street. According to Peter Berezin of BCA Research, the market is experiencing a pronounced K-shaped trajectory, with data spanning over three decades showing a widening performance gap between company tiers. Profit margins for the S&P 100 mega caps and S&P 500 large caps have rocketed upward, with mega-cap margins recently pushing past the 16% mark. In contrast, the S&P 400 mid caps and S&P 600 small caps have seen their margins stagnate and decline over the last few years, currently hovering between 4% and 7%.