was or were

Benchmark salaries was introduced in 1994 to formally peg ministerial salaries to the market. Right now, the annual salary of an entry-level minister in political office is pegged to two-thirds of the 24th highest earner among a group comprising the top eight earners from six professions. The professions are bankers, accountants, engineers, lawyers, chief executive officers (CEOs) of Singapore manufacturers and CEOs of multinational corporations.

Shouldn't it be "were" instead?

Thanks.