It seems a bit odd that both activities are described as a "club" and involve physical activity, yet taxed differently.
So, it is not the state of New York that is taxing the yoga salons, but New York City. Some states and their cities do not have the same sales tax base making compliance even more difficult for vendors! Per the 2011 Tax Bulletin:
"New York City imposes its local sales tax on every sale of services by weight control salons, health salons, gymnasiums, Turkish and sauna baths, and similar facilities, including any charge for the use of these facilities. This tax does not apply to any of these facilities located outside of New York City. Therefore, dues, membership and initiation fees, and any charges paid for the use of these facilities located in New York City are subject to the New York City local sales tax. However, if a facility also provides access to participant sporting activities and facilities, such as a swimming pool or racquetball courts, to its members, the facility is not considered to be a weight control salon, health salon, gymnasium, or other establishment for New York City sales tax purposes"
How to simplify? Apply sales tax to all goods and services consumed by individuals as final consumers and lower the rate. Perhaps some necessities should be exempt such as non-elective medical services. I suggest taxing food and finding another way to provide relief to low-income individuals such as through a refundable income tax credit or provision of debit cards for use throughout the year (ideally attached to the cardholder's bank account including accounts paid for by the state). The reason is that higher income taxpayers spend a lot more on food so exempting it provides a big tax break to individuals who do not need it. With this design changes, we would not have oddities of knowing whether a yoga class or health club dues are subject to tax - they would be because purchased by a consumer.
What do you think?
More - see 21st Century Taxation website - here.