For each main industry, what is the total number of companies for the industry with the highest total market value?
SELECT main_industry ,  count(*) FROM company GROUP BY main_industry ORDER BY sum(market_value) DESC LIMIT 1
SELECT main_industry ,  count(*) FROM company GROUP BY main_industry ORDER BY sum(market_value) DESC LIMIT 1
[{'Main_Industry': 'Oil and gas', 'count(*)': 5}]