The National Council of Churches reports on denominational statistics, with the numbers for the 25 largest denominations (the Seventh-day Adventist Church might be number 26, with 1,000,472 members in the US–15,000,000 in the world).
Mainline churches continue their decline, including the ELCA. See a bigger picture of its downward trend here. It started in 1987 with 5,288,048; 20 years later it was down to 4,709,956.
Can you really do a comparison? No. The churches listed count membership differently. Some include infants while others include only adults. Churches are self-reporting–and some individual congregations don’t have accurate rolls.